Heartbroken. What should I do?

So last week me and my fiancé had a rough week. We fought everyday about stupid stuff. I’m going through a lot. Found out my pregnancy is a blighted ovum. And now my younger sister is pregnant after I’ve had now 5 miscarriages. And I’m depressed from all of it. Well we got in a fight and I went to stay with my aunt while things cooled down. Well One Friday I found out he wasn’t where he said he was. He was “with his friends” well then all of a sudden this girl pops up on his Facebook. I asked him about it he said he think Corey his friend looked her up. Okay that doesn’t make since. Well then he friends her. So I feel like something is up so I start asking more questions. Apparently his friends wants him to be with her and all this and that. Well he kept telling me he never messaged her. Well I went through his phone and found a message her sent to his friend asking if I ruined his chances with this girl because I messaged her and let her no that I am pregnant and that we are still together. Well his friend said no sir and then he asked has she said anything about me. Well I hacked into his Facebook today and found this

A secret message he sent her the Sunday I CAME home. No he hasn’t messaged her or gave her a second thought. I confronted him about it and he turned it around on me saying everything was going good till you went to snooping. And that I’m ruining us and all this and that. I only snoop when I feel like something is up and my gut told me to look. My grandmother always said “listen to your gut your heart is stupid” so I looked and found it. He then went and blocked her today..... what do you ladies think I should do. Should I forgive him work on us and move on or forget him and leave???