This was my SO's life before I came along and said HELL NO. Idk how long you have put up with this BS, and if it's been years of you just keeping quiet and "rolling with the flow", it will likely be harder to change. I put up with it for about a few months, and when I discovered the depth of their dysfunction, I just couldn't deal. My SO has changed to a week-on/week-off, with changes only when there's a damn good reason (BM wants to go shopping isn't one.) It wasn't easy and it took me walking out of a dinner i cooked after BM walked into the house without knocking, plopped her a$$ down at the table without looking at me, and started eating off SS's plate. No way should you have to deal with calls and texts between your DH and BM at all hours of the day and night, especially when what they are talking about affects you and you aren't allowed to know what's going on. Hill to die on. It will probably take marriage counseling to undo this tangled web of shite. 

Stop doing anything for your dh or his son. He is behaving as if he had no obligations ... See how he likes it when you do the same.

Not your monkey...

He needs to be more afraid of YOU than BM.  Make it very difficult for everyone when they forget to include you in the plans.  Didn't make enough food? That's what you get for not telling me , here's a coupon for fast food.   Disrupt our date night? No nookie for you.  Plan your life and stop making adjustments.  Don't tell him of your new rules just implement them.  Let him feel the pain of choosing BM over you.  Men caught up in pleasing an ex need to be shown the error of their ways in the most extreme way.  At 14, SS would probably do best with week on week off schedule.  Might stop the bed wetting too you posted about before.  Stability is a good thing and you are right that BM gets off on the chaos.  Disordered people are like that.  

Take yourself out of the crazy then. If you don't know he's coming then don't scramble to cook more for them. Your DH will have to figure it out. No re-scheduling cancelled plans or suddenly having to change them. Plan for yourself only - your DH can plan everything else. You don't drive, make extra work for yourself or anything! 

When my YSDalmost17 pretty much ended her regular week on/off schedule with the parent's apparent blessings, I was frustrated like you were. Then I just stopped. I don't help at all any longer, partly due to this unpredicable timing. DH has to shop, cook and clean up after her when she's here. He has to plan stuff. There's more to it and you will likely find that out too but this is your start.

I know I'm old school, but when I read about some of these co-parenting schedules you guys have, I really don't know how you do it.  We initially had the 3 SKs every weekend and most of the summer and the transition period was bad enough, I'd hate to think if it had been any more complex than that.

I suppose the co-parenting schedules give the kids a fairer access to dad but it must be tough.

I would think that at 14 a week on/week off schedule would be age appropriate.  Or 2/2/5/5 if you wanted consistency on weeknights for job or activities purposes. Schedules where the days keep changing or the parents keep swapping days are crazy for a kid that age - there's no need for that kind of chaos. 

Since you've expressed your thoughts to H and he hasn't managed to do anything about it, you might try full disengagement and cooking for 2 every single night until DH figures out whose needs he should be catering to. 

You might also try to get your DH to consider that bouncing around at the whims of his parents, never knowing where he will be sleeping on any given night, is probably not good for SS. If he seems immature for his age and doesn't have the same social and self-sufficiency skills of his peers, it may be due to the lack of structure in his life. 

That poor kid! Not only is he treated like a baby but he's passed around as if he were an object that simply needs to be placed somewhere, kicked around like a football. How on earth can he be expected to function normally? After TEN years of this nonsense, he's still confused about it. How about his parents grow up and start to take their son into consideration when they are happily switching days around to facilitate THEIR schedules and lives? How about they try to make life more comfortable for him? Do they seriously expect him to get through high school while living in total chaos? How will he ever get his homework done? Gawd! Have they no respect for their child?! How is he ever going to gain any self-respect if he thinks he isn't even worthy of consideration by his own parents?

OP, I don't know how you do it because YOU are being disrespected too. Your husband should be ashamed of giving priority to his ex-wife over his actual wife. It's time he started turning his phone off at night and switching it back on again in the morning. She won't die. Don't forget to switch yours off too because that's the next thing she'll do - call you. Simply stop making dinner. Point to the bread and the sliced meat/cheese/whatever to make themselves a sandwich when they get home. Not your responsibility.

Let DH know you are not happy with being left out of your home's routines & you are going to do something about it, even if he won't. Start putting yourself first, right now. Do your own thing - if DH can schedule without consulting you. You have the same autonomy. Make dates with Girlfriends, go to the gym, hang out @ the coffee shop, take a class. Anything not to be at home during this chaos.  

Let DH know he is stunting SS's growth & you won't live with a non-functioning adult. How does he expect SS to go to college in 4 years if he has no independence. What is his plan for SS to leave the nest when he can't even remember where to be on a regular basis? 

Afternoon from college or university. Hubby never told me and i made him give me a heads up. Ss would always notify hubby last minute like an hour or so before ss was due to arrive home. 
 

before that i just did my routine as normal. I didn't go out of my way to cook for him especially because he always bought take away. I just cooked what me hubby and our 2 kids ate.

I remember when our daughter was over a yr old and eating solids and ss told off his dsd why is she eating solids like i'm a bad mum and hubby told him she's been on solids since months ago and toddlers eat veggies etc too- that shut ss up

i cooked food for 3-4 people most days and often there was some leftover that we'd keep in fridge, it was upto ss to reheat.

there were some times hubby requested i make a special dish for ss to which I immediately replied with "No!! I don't go out of my way to make rude, selfish and disrespectful people feel welcome or special when they treat us like crap and it was real selfish and rude of hubby to demand this of me" that shut hubby up real quick

Or at least one who can and will effectively manage the baggage.

If you will not move on, at the very least shut off notifications.  How hard is it to turn off notifications during your stipulated black out times?  Make that happen. Make DH shut his off too.

Leave BM hanging and make sure she is on the hook for child care if she will not contact DH during reasonable hours.

and the visitation schedule. Co-parenting really does not have to have anything to do with the specific visitation schedule.

Co-parenting IMHO is more about aligning on the behavioral aspects of parenting than it is about who does what and when.

Each parent is responsible for the care, feeding, and trasport of the COD when the COD is with that parent.

IMHO of course.