I admit that someone losing her child because she was too strict with them is a first for me.

"She accesses him of lying, of being messy, playing games with her "

So, tell me, does he lie, is he messy and does he play games with her? And what are you dong to try and change that? And how thin are your walls if he has to "creep around" to avoid waking her? Isn't he overreacting a little bit there? Also try to put things into perspective - you admit he's a bit troubled but not a terror (in your opinion). Few people are as candid with other people's children as they are with their own. Maybe the "bit troubled" is overwhelming for your gf?

No offence intended but I'm not sure you are ready for a relationship yet if you feel you have to protect and put your 13 yo first because that means shutting out your gf and basically putting her last. What kind of a relationship would that be?

It is hard to know where "a bit troubled" meets the ways you accuse your gf of behaving.  But if you "communicate really well" can you address this with both of them?   As far as creeping around the house goes, as long as it is not after 9 or 10am in the morning, then I would see at as polite not to make excessive noise. 

You acknowledge that you may be overcompensating on two fronts - a) because of your own troubled childhood and b) because you feel guilty about your first marriage.  It is never a good idea to overcompensate - children do not benefit from being spoiled or overly protected. 

A couple of issues. You say your ex was very abusive.  In addition to that you had a troubled childhood. It seems you still have not addressed your trauma. Just from the things you have said and your feelings related to them these things are still very much a part of your everyday life. 

You have only been in this relationship a year, that is still not enough time to really know someone.

Putting your SOs actions and behavior aside. Are you ready to be in a relationship yet? Perhaps you need more time to work on yourself, perhaps attend therapy. You will be a better father and partner once you have spent more time working on yourself.

Things were great, the kids loved her and we got on really well-

I read this often on here. It's really not surprising when a relationship starts out great but a year or so later it's not working. That's because you two have started REALLY getting to know each other. The newness and excitement have died down. The point of getting to know someone is to find out if your compatible right? Sometimes the answer is no, but it might take awhile to see that. If this person and your life are not truly compatible, don't force it and make everyone miserable. This is not like you two just have different taste in music. You have fundamentally different expectations and views on parenting and family life. That's a big deal! Either get on the same page or keep looking for someone who is better suited to your life. I don't think you can expect her to completely change her views on parenting (right or wrong) for you. It sounds like a recipe for resentment. It doesn't really matter which of you has a "better" style of parenting, the problem is your views are not compatible and that will continue to create stress for everyone especially your son.

On a side note, if what you say is true about driving her own child away why would you want someone like that around your child? It kind of sounds like it's bound to create problems.

I'm sorry but this sounds like a much bigger issue than just her crabbing at your son.

Neither of you is ready for a relationship that involves merging lives. Dating, sure. Anything more serious than that seems too much right now.

You both have trauma for different reasons, but you both are also contributing to that trauma. My guess is that you give in too much with your own kids because you're making up for their crap mother and your own childhood. That's fine, so long as your kids can adjust to that level of freedom and giving. Your oldest did; your youngest has not. You need to change your parenting style FOR HIM even if it isn't what you wanted to provide.

Your GF likes structure. Your son would probably benefit from more structure. Unfortunately, she has taken it way too far, to the point of potentially mentally abusing her own kid. If she is still actively grieving that, then that tells me she hasn't done the work to improve herself, so she certainly shouldn't be around other kids in a parenting/mentorship role until she does (if ever).

Your son is struggling. He needs your attention. Your GF is struggling. She needs to get her own help. You're struggling. You need to get your own help. Can you balance all three of those and make/encourage/hold accountable the changes that need to be made? If you can't (and a lot of people couldn't), you will need to look at cutting one of things out. For your son's sake, it can't be you or him.

I am in the same situation. Difference only one- I am a stepmom. But feeling same what author of this topic mentioned about his new life partner. I don't want people to think I am arogant or something,but with my bf its same - his ex and he has very bad relations. My bf had very bad childhood. Now he is compensating. When comes to his kid - you can not say anything negative. If I will say - put other pants,these are too small. He will accuse me I am calling his kid fat. And many other things. I am struggling a lot,and also I am not an angel - but I can say that those struggles coming 95% only because of him. He is spoiling his kid like crazy because he is competing with ex. I mean all I see just bad raising example. Thats why I dont even want to be around them and finding excuses to go away for a day just not to see this. Sometimes its like hell.

I suggest for author not to make fast decisions and talk with her,give a little bit more time for everyone. I know how you feel and I know excatly how she is feeling. 

By the way,if your son is really like this,like she is saying,if I would be her and it would be 100% truth,that he is terorising me,so I will record everything.