Paranoia

My ex-bf was an *******. He used me for sex and later when I broke up with him he came back to rape me.
I always have had trust issues, but this didn't help me at all.
I found myself a new bf and that's when the real trouble started. I do not trust him, and when I do I will push him away, just in case I cannot trust him after all.
It has gotten to the point I would just look for any evidence to support the theory my bf isn't to be trusted. I accused him from still being in love with his ex, when I found out his password on his computer was the nickname of her. Actually I still believe this wasn't a coincidence, but what am I suppose to do? Keep on pushing him away?
Once I looked through his stuff when he was away, to make sure there was no monkey business. In my mind I have even doubts about his friends and the way they act towards me.
It's one big paranoia mess in my head.
There always seems to be this little voice inside my head that wants to see the negative of his behavior or the weirdness in what he has said.
Once he told me his pet died and a split second my mind asked me if he hadn't killed it himself.
It's exhausting and it is starting to screw up my relationship. Any advice?