Thank you OP 
I think sometimes counselling, CBT and other therapies can help some people, although for many it's just too much, too painful and something many are never ready for/able to do. One of the things that has helped me, is to abandon looking for a resolve, I got to the point where I didn't care why I felt like ill, I just needed to feel better. I found that searching and the going over of my life in therapy just made things worse - I had several therapists - I think I got the point where I thought, even if I understand why I feel like this, I'm still going to feel like this so how do I make it go away.
I initially started medication to give me a break from myself/the pain; with a view to get to the bottom of it when I felt stronger. 11 years on, I couldn't care if I never "work through" my issues and come to terms with why I have depression. It's quite an empowering place to be, I honestly don't think there's anything wrong with being on (the right) pills forever 
You sound like there's a lot going on for you at the moment. There's obviously those awful memories from the experiences you've had, the feelings they conjur up which are made worse by the very present effects of the breakdown of a relationship.
One compounds the other, I'm terrible if faced with a difficult time, I group all of the bad things that have ever happened to me, along with my fears - together and become enveloped in all that sadness/hopelessness. (I think that's quite typical of a depressive thought process although I only know my experiences)
Id be so overwhelmed in your position, by what's happening with your partner, which is bound to dredge up a lot of other negative feelings you've had in the past and it all just piles up too high.
I would probably go and see the GP. Don't feel you have to pour your heart out, just tell him/her you have a good insight into your own mental health, you're having an excruciatingly difficult time and you're a mum and you need to feel better than you do.
If you want to try and see if meds can give you a break maybe? it's exhausting feeling as you are right now. I think it takes about 3 weeks for an ssri to take effect ...