My boyfriend is a sex offender

My boyfriend is 22 and we've been together 10 months I moved in very fast because of my family pushing me away. His niece is 12 years old and her best friend is one of the neighbors who is the same age maybe 13. When we first started dating the neighbor would never hang out with us like the other kids she would just stay in another room of the house. After a month she started to hang out but one day I went over after work and I was talking to him on the phone and asked where his car was he said his sister had it so I went inside to find the neighbor in his room standing next to the bed and he was lying down playing on his laptop but the door closed and the lights off. I confronted him later and told him it looked wrong and very suspicious. He also told her that I did not wanted them to be alone and thought the way I found them was wrong. She pulled me to the side and told me she had trouble talking to people and was comfortable with him but she also said that he accidentally pushed her to the refridgerator and when he hugged her to comfort her she said he asked if she liked him and she said she thought of me and said no and gave me a hug. I told my boyfriend what she said and he told me that he did push her into the fridge by accident but he does not recall asking her that. Well at least a month after that I saw he was messaging a username lonely on kik and even though I dont like to snoop I looked at the messages. And the neighbor was telling him that the kids were all sleeping and she wish he was there and even worse he responded for what. She told him he should sneak out when im sleeping and she sleeps over. He neither rejected or confirmed doing so. She told him that I follow him around as a lost puppy and he didnt even say something to defend me. I confronted him again and he said that they didnt go out but they kissed before we started dating he told me he would answer all my questions honestly and that they didnt have sex.  He felt guilty that they kissed when we first started hanging out but he was only leading her on from kik to see what she would say knowing he has a gf. He said he texted her that they shouldnt talk anymore but deleted the messages. So after that I never wanted to be without him I didnt want to go to work in the case that he cheated on me with this little girl. I was always paranoid that I would come home and find them together. I never did but I was worried all the time even if he went to the kitchen to cook. I went on vacation for a week with my parents and the day I came back she kiked him saying hi. She kiked him a lot saying hi (at least once biweekly) whenever I did look at his phone. We always had issues with her. Then she kiked him never to write her again about two months ago and I asked why would she say that if you giys havent wrote and he said idk. I had to ask repeatedly if he wrote her and he said his neice told him that the neighbors step dad molested her. Which he has heard before and wrote her to see if she was okay and told her we were moving I asked why did he need to tell her that. He just summed it up as he cared and he was noisy. And finally we moved away to my sisters due to money issues and after me still being worried because she still kiked him on Valentine's day and a week after that he finally told me that he fingered her and that was the lonfest night because I finally looked at him different and a week after that he told me that she just wanted to kiss but he convinced her to be fingered but they didnt do nothing else. Im scared to even find out if theres more and I feel so betrayed and I feel like I cant leave him I recently found out I had Herpes and he stayed with me I wouldnt eant either of us to spread that disease bit i cant even have sex with without thinking of what he did... I really need help processing this.

I would report your BF and this girls's neighbors step dad to child protective services as well as the police. Having sex with a minor is against the law. You say " I feel so betrayed and I feel like I can't leave him" You need to start growing up and realize that you need to respect yourself you can do better than a child molester.

Damn right.