I'm stuck in a rut

[Greasley2k15]

Hello all, I'll try to keep this brief. I've came out of a 9 year relationship with the father of my three kids. Throughout the relationship I was cheated on and emotionally abused. It took me up until last year to realise it was abuse. Now at the beginning of the relationship we were as happy as could be but he cheated the first year which devastated me, I stuck with him because I had hoped he would change his ways obviously 8 years down the line guess what.... he hasn't. We've only had 1 good year where he hasn't cheated.

I've found someone who makes me happy and tries his hardest to help out with my children and my mental health but I still feel a massive hole in my chest. I know deep down thst the relationship was toxic and it was in part to thst, thst I ended it with him for the kids and my own sake. I just can't shake the feeling of depression. Obviously I had set my mind on him being the one and only guy in my life. I never wanted a broken family and it hurts knowing its eventually come true. I feel guilty on behalf of my now new partner because I feel like I shouldn't be having these feelings of missing my ex, I've been told it's a natural thing but everytime I think of what we had and did, it makes me upset and emotional and all I want to do is curl up in a ball and cry under my duvet. As you can imagine my partner tries to console me as much as he can. But again I just a little bit of advice and help through this please I'm stuck.

That's a long relationship you were in, and one which was damaging.
You've been out of it only about a year from what you said here, so you've not had a lot of time to emotionally recover before you're investing and engaging in a new relationship.
New guy sounds supportive, but if he tries to shoulder this with you, it's a tough burden to place in a new relationship and there is a risk it will spoil it, or your red flag radar might still be off leaving you, and by extension, your children vulnerable to an unhealthy dynamic (he might have a bit of a saviour complex for example, which, in the long run, isn't what you need to become strong within yourself)
I think you need to give yourself time to heal from your ex. You need to reflect and think it all through until you can get to the point where your emotions aren't so fragile.
It takes time to heal from something like this.

I would try to seek out help for recovery from your ex away from your new relationship as much as possible.
Friends, therapists, books, whatever it takes to work out all through and start to find new ways to live happily despite life not turning out how you, understandably, wanted.