Ex got me pregnant - HELP!!

Just wanted to share my experience and get some advice:

I was with a guy for a year or so, everything was perfect, he moved into my apartment after 5 months, he was even willing to take on my son as I was with his 2 kids. I was completely in love with him, as I thought he was with me. He used to say he wanted to marry me and have kids with me. We were even looking at houses. However a few months after he moved out back to his own apartment, convincing me it was so he could spend quality time with just his kids.

A month later I found out I was pregnant - I wanted to keep it, but he didn’t. He wanted me to have an abortion. His reasons being was that we had plenty of time to have babies, he wanted us to go on a big family holiday later in the year, get some money behind us and a bigger place to live before we had a kid together and that we would try again in 12 months or so. I told him I wanted it but then he started getting nasty saying that he would cause so much stress for me that I would lose the baby anyway and I’d be left with nothing. I was head over heels in love and wanted to be with him so I reluctantly had the abortion. After that I thought things were great, had a lovely family christmas, he even told my son and his 2 kids that they were all going to be brothers and sister. Had the best new years eve ever and when I was out shopping he’d tell me to look at engagement rings…his 5 year old daughter was helping me look at them.

Later that month there was a rumor going round that his ex girlfriend was pregnant with his baby - he instantly denied it, told me it was her causing trouble. He started getting distant with me and eventually finished me - saying that he still loved me but just wanted some space.

A few days later I got a text off his ex saying “leave him alone he isnt interested in you lol”. So I figured he’d started seeing her and that was the reason he finished me -I was gutted

3 weeks after he finished me I found out she was pregnant - 6 months pregnant with his child and they had already bought a flat together. That was the real reason he didnt want a baby with me - it turns out I was used the whole time as a big plan to make her jealous and want him back. She knew he was with me but didnt give a toss, she found it quite amusing. The whole thing has seriously messed my head up - I’m on antidepressants, anti anxiety pills and even sleeping tablets. I’m still obsessed with him 4 months down the line - and now she’s had the baby (in the same week that my baby was supposed to be due) its a lasting reminder of what he did to me and makes me feel sick.

I’ve still been sleeping with him. He even had sex with me when she was in hospital the day before the baby was born. I know it’s messed up, but the only thing that makes me feel wanted by anyone is when I’m having sex with him - although I feel 100 times worse for it when he walks out of the door to go back to her.

Now I’ve just found out I’m pregnant again. There is no way he’s bullying me into getting rid of this one.

Should I tell him?? Should I tell her?? Or should I just get on with it by myself??