She’s making me crazy.

I met my fiancé back in August of 2016 right before his divorce was FINAL... we dated for about a year then moved in together shortly after that I found out he cheated on me with a family friend he grew up with, she’s pregnant and is claiming the baby is his... we get through it the baby is NOT his thank god! So then in October of 2018 we had a falling out and he ended up temporarily going back to his ex wife and mother of his child... he won’t leave me the hell alone the WHOLE time, she says she doesn’t care if he comes back to me but she doesn’t want to have to transport their kiddo back and forth as I had moved 2 1/2 hours away... well he ends up leaving and coming to be with me in early December 2018 and we find out the DAY he comes back that she’s pregnant with his child... seeing as we’ve been trying to conceive since the end of 2016 I’m very hurt and now I have to go through this AGAIN... she says she’s getting an abortion but doesn’t, well she’s having a boy. My mind state is so messed up at this point I’m hurt I’m mad and I’m resentful. This is literally tearing us apart... I know we were broke up when she got pregnant but it hurts just as bad. I adore his son that they have together but a new baby??? After me? I feel like I’m losing it, we argue and I end up shutting down every time. What the hell am I supposed to do, I know he ain’t shit but I love him and he’s like my best friend. I know I have to let him go but somethings always holding me back and I don’t have the heart to hurt him the way he’s hurt me. Why is this my life? ☹️😭😤