DH never flat out told her to stop trying to talk to him about anything non kid related. He did stop replying and quickly hung up on the phone if she started that crap. 
 

I did tell him I found it offensive that while they were married he wasn't good enough to be her "best friend" but all of a sudden he was suppose to be a available for non child related emotional support. I also told him to let me know if he wanted to be in an emotional relationship with BM so I could go find boxes to pack my shit and move. 
 

I really would have moved and broke up with him if it continued. She got the hint and hasn't tried again. She is also happily married  now. I honestly hope it's a successful marriage bc it keeps her busy. 

Finally I reached a boiling point and forced him to text back “please can we limit communications to necessary issues regarding g our son”

You shouldn't have to force him, he should have been doing it on his own, all along.

Its a big red flag that your DH tolerates and excuses this behavior.  My DH will just hang up on BM any time she goes off topic.  A few years ago, BM sent my DH a love letter and mix tape.  This was after we had been married.  DH and I actually laughed about it.  Then he had his attorney send a letter threatening a restraining order if she kept unnecessarily contacting him. 

Having a child together is not a valid excuse to let Bm continually overstep boundaries.  If your DH will not stop the contact, then you have to decide how much you are willing to tolerate before you throw in the towel.

Oh, yeah. Your SO is still enmeshed with BM. YOU had to FORCE him to text BM??? No bueno.

You know this is inappropiate.

What are you going to do about it if he continues?

You could be passive aggressive and start texting YOUR exes.

Or you COULd have a nice succint conversation, each time it happens. Toxic Troll used to text DH inappropriately, almost "sexting level" inappropriate. He didnt tell me until I caught one. He claimed that he nevr responded to her drunken texts, however, when I caught the one, I went BALLISTIC. No passive chit. ON HIS OWN he texted her that Clove is not happy with her texting him certain things, and please stop. She thought it funny and texted him "wow, shes got a problem with that? Well at least MY boyfriend isnt jealous of MY ex".

About a year after that, her bf Tweedle is calling my DH while we were at a concert, crying because shes not coming home at night and shes "with" other guys and they are living togther still. LOL.

So, now, when Toxic Troll texts DH something non skid related, I tell him (repetively) he doesnt need to respond. I tell him do not text her back immdiately because he is not at her beck and call. Im 5.5 years in, and she still tries to involve him in her dating life.

I hate it.

Fortunately I've never had to deal with this, because BM has no interest in DH.  She cheated on him multiple times and she left him with no regrets.  She has always had a boyfriend (now she has a husband) since she left DH and she has plenty of friends and family, so she has no reason to communicate with DH about anything other than the kids.

However, you don't have to experience it to know that this is WRONG.  There shouldn't be cutesy, flirty messages between your SO and his ex.  He shouldn't be FORCED to shut her down; he should have done this on his own once these messages started coming.  He's in a new relationship, so unless his new girlfriend is fine with it, he doesn't get to have an ongoing relationship with his ex except for what is necessary in connection with their mutual child.  You're not overreacting, this is inappropriate and disrespectful of your relationship.  It's unfortunate that your SO can't see that on his own, but if he allows any of this to continue AFTER you've expressed your displeasure, then either he values his relationship with BM too much or he has no balls (in which case I'm not sure why you'd want him).  IMO, this is a hill to die on.

OP, if your SO wasn't okay with this, he'd stop it himself. BM isn't the issue here.

gas lighting you.

Facts:  "DH, you are participating in interactions with BM that go beyond what is skid related".

Your Interpretation of the Facts:   "Because of this, I assume you are still in an emotional relationship with her".

Your Result.  "I cannot be in a marriage with someone who is still emotionally connected with another woman.  So either we 1. get counseling and try to resolve it.  2. We divorce.   There is no option here where this can continue."

Facts:  "You're now deleting all of your phone records with BM"

Interpretation of Facts: "I can only assume its because you want to hide your conversations with her from me because they likely cross boundaries".

Results:  "I can't be married to a man who feels he has to hide conversations with his ex wife".

The thing is, and i say this gently, you have to decide what kind of relationship you want.  Then be brave enough to walk away.  You dont have the power to change anyone else.  All you can do is change how you react to it.

It sounds like you desperately want to stay married.  Clearly you're miserable.  Talk to him.  "DH, because you keep hiding conversations with BM from me, I can only assume you are still very much emotionally connected to her.  I want to stay married to you but I can't be married to you if you are still attached in that way to her.  If we don't get counselling to work through this, then I have to leave".  

It can't be just a threat to leave.  You actually have to be prepared to end it.  If you're not ready to walk away, then you have to figure out a way to deal with it. 

Are you married---???? I know you have 2 kiddos with him. Its not ok for those two to be flirting.

First:

Here is what I would do. I would go to your cell phone store AND get a print out of all telephone calls. You wrote your paying for his cell right? Well---you own the account.

With a yellow highlighter---mark each incoming and out going call to his ex. THEN you can determined if in fact your boyfriend is calling her or not AND deleting the calls. Collect all your facts then make a decision. Oh and I would keep your data under wraps for a little while. LETS see how long he is willing to lie. I would check on Novembers records too.

You have 2 children...go to social services  Just for information gathering.... See if you qualify for reduced or free housing, food stamps. HE Is going to have to pay you cs too. Go on line to the cs calculator...punch in what you can $$ and you will see what he may own you.

Good Luck...I am sorry---he should not be doing this.

JMO

The fact that he is now deleting and hiding the messages is a HUGE red flag.  That would be a deal breaker for me.  I would tell him to go back to her and keep her happy like he wants and peace out!

He doesn't seem very trustworthy. He needs to pick a team. Probably loves the attention and the thrill of sneaking around with the texts. If he's deleting them, that would seal the deal for me. So f-ing disrespectful! Especially considering you have been togehter for so long and have kids together. (not that this crap is right under any circumstances)

Turn off his phone and see how he likes that. Just kidding, that's petty and immature

Your marriage sounds a little crowded. Did he forget the part about forsaking all others? 

Yeah I wouldn't be able to deal with that either. 

In the early days of our relationship BM tried to see how far she could go. My now DH would answer her calls and if it wasnt about SD would say "since this isnt about SD or an emergency situation you can email me" and hung up. There was a while he refused all contact via phone or text, he would reply via email in the evening. 

To be fair to BM she had an understandable freak out. I think she was worried I wanted to play mum, as soon as she realised I had no such desire she calmed right down.

But its again your DH that has to nip it in the bud.

SO thought this is perfectly ok and I’m bonkers and must accept that she is “the mother of his child”.

"DH, I can assure you that, when we're divorced, I certainly won't be sending you stuff like that."

Make him sweat ...