My boyfriend stopped all contact with me and started dating his step cousin.?

[Krissy]

I'm going to try and summarize this long story.

I started dating my current bf about a year and a half ago. In the beginning of the relationship he was a BIG flirt, he flirted with girls on the internet. I had to tell him a few times that this wasn't okay. I forgave him each time. Then one day I was browsing his Reddit page and saw he had a posting asking for advice, he wanted to know if he should pursue a relationship with his STEP COUSIN! I couldn't believe what I was reading,,, Right then and there I told him I saw the posting and it was over. A few months went by and stupid me got back with him. He claimed it was a mistake, he didn't know what he was thinking.. blah blah blah. A few months later I went on a cruise for 9 days, I had no contact with my bf, when I came back from vacation and had my phone once again, messages came through from my bf saying he thought he may be gay and kissed a guy, he said he was confused and couldn't talk to me about it. I didn't try to contact him of anything,,, I jumped into a new relationship about a month later (tried to forget about him) this was a bad mistake because 2.5 months into my new relationship I started missing my ex, I realized I never gave myself time to heal, I jumped into a new relationship with a guy who wasn't even my type., I ended up sending my ex a friend request on facebook, but deleting it a few seconds later. My ex got the friend request notification before i deleted it. We started texting, I ended things with my new bf and began talking to my ex again. He lied about the whole kissing a guy thing and being gay, he actually went out with his step cousin.. I kind of just forgot about the whole thing, we never really discussed what happened until lately.. (3 months back together) I feel stupid, I don't understand why I keep running back to him. I feel a connection with him that I don't feel with anyone else. He claims he will never betray me again. But I'm not sure If I believe him, I don't fully trust him. Do i need to once and for all move on? I desperately need advice. Thank you.