I hurt inside.

I've heard so many opinions about what I should do.. I didn't care about what anyone thought. I needed to know for myself that I was doing the right thing for me.
I thought I could eventually get past this heartache and just be happy. I had an occasional happy moment or day with him, but for the most part its not getting much better. I just don't trust him. Someone told me that for the relationship to work, I have to let it go and not look back. I just don't see how anyone can do that. It's too hurtful and damaging to just forget.
Whenever I bring up the issue, he's too tired to talk about it, and asks why am I still bringing it up. I don't get how he could expect me to just act like it didn't happen. FUCK I'm hurting! I find myself trying to monitor everything. I wonder if while I'm gone there are girls in our apartment. I wonder if when he's out he's texting girls or hanging out with them. How can he not understand that HE DID THIS TO ME.
I know that my constant interrogation is nuts. He tells me he's not doing anything wrong but what credibility does he have? I don't want to make him miserable. I tried not to think about it, but its nearly impossible. I always come to the conclusion that he doesn't truly care about me and love me. He's so selfish and immature. He never thought of us as one, it was always him and then me. He would always say we have our separate lives and then our life together. We'll I get what that means now!!! I'm so disgusted and to make things worse, he's in the wrong but he makes me feel bad about it. He makes me feel like I'm not making him happy. Well FUCK THAT. I deserve better, I'm a fucking damn good girlfriend. It's gonna be tough to try and get past this, especially seeing how we live together, but I know that in time ( a lot of time ) he'll be completely out of my thoughts and someone new will love me and love me right.