Love triangle? please help!?

Hey there. So, the long story.. I'm in a relationship with a guy and been with him for 1 and a half year and been living with him for 2 months, but I've fallen in love with one of his good friends about 3 months ago! this is how the story goes, like we met when he came to me and my bf and his friends to chill with us and we introduced ourself probably but few months before that he randomly added me on fb and was flirting with me asking to meet him but obviously i turned him down cause i had my bf, he said he didn't know i was his girlfriend even though there were pics of me and my bf on facebook... anyways when we met face to face, we recognized each other and started talking.. then he would msg me on facebook and i would chat back, one night i told him im going out for a cig (i cant smoke inside the house) and it was dark and cold and asked him if he would call me for 2 minutes to chat, because i didn't wanna disturb my bf who was sleeping by calling him and he said ok and i gave him my number, i thought it was harmless and it was right? but the thing is.. he started calling me more and more and we would just talk on the phone for hours about random stuff and life.. then like 3 or 4 days later he told me that he loved me :S i must of had a crush on him before but after he told me that, i fell in love with him too.. so the fast story.. he would always come to my and my bfs house when we moved in together, he would always get jealous whenever i bf kissed me or touched me, yeah he started hanging around with us like everyday and me and him would keep in touch by fb... so like he changed.. he stopped coming over everyday, he lives in a different city now, i learned from a girl on facebook that he used to be her ex and he cheated on her, brought different girls to the house when she was out and just plays with so many girls.. what she said did have evidence.. and all his friends would say he is bad, including my bf. i guess they were right cause when he forgot to log out of fb i checked it and he said to so many girls oh i like you a lot bla bla.. so yeah, obviously he played me.. but i feel so down about it.. he told me that he loved me? and now some of his friends tell me that he said to them that i love him? and apparentley he said to one other that i had sex with him? which i never did but i did do things with him and kissed but i didn't have sex with him.. ive spend 3 nights with him but not in a row but i didn't have sex with him.. and now i feel guilty about my bf.. especially since a few of his friends know about the affair and god knows how many else.. i don't know what to do, i wish that i never met this guy!!!!!! please please help? any advice?