Haven't been on in a while.

Was doing really well. NC works a treat. However I was silly enough to take a call from him (so he could talk with his daughter but ended up talking to him after). All the usual crap about 'oh I can't afford a lawyer for mediation' 'ill do whatever u want so that I can see (our daughter) just drop the lawyers' blah blah blah. It's all crap. It was just him taking whatever chance he could to tell me about his life.
He doesn't have money - cos he's saving for a house (with OW)
He's moving (with OW) back to the town we used to live in together.
He doesn't want to visit his daughter where we live because it reminds him of me and he hates that.
He's going on a holiday with OW and his entire extended family and wanted to take our 9month old.

And of course, as always, he placed all blame for everything back on me. (Which I know is crap and that's just to make himself feel better).

I've been doing so so well. SO well. I've started studying, I've made new friends. I've kept him out of my constant thoughts and wen he does pop into my head, it's only for a fleeting moment before I move on to the next thought. I stopped talking about him, saying his name, seeing his face where've I looked. It was bliss.

But, now, after the phone call my head is spinning. My emotional scab (that was healing) of anger and hurt is freshly reopened and overwhelming. Do I want him back? Absolutely NOT. It's quite the opposite, yet just as destructive. I'm full of regret. I find myself not constantly thinking of what I did wrong, or why doesn't he love me (as I've done in the past), but I'm now stuck in evil fairy land thinking about how much I regret the day I met him and if only I could go back and change the doomsday. Every day I'm filled with regret that I met him. I regret the last 5 years.
I am taking the necessary legal steps to sort out once and for all (it's a very long process it turns out) custody arrangements for our baby and I will not back down as he requests. But honestly, I hate that in one phone conversation with him, I feel like all my hard work has gone down the drain, and I feel myself slipping back into the feelings of hopelessness, anxiety, stress and lack of energy.

How do I stop this line of thinking, leave the conversation as a 'void' and pick up where I left off in my happy life before the stupid phone conversation?