My boyfriend cheated what do i do?

I just found out that last summer when my boyfriend went on a trip with his friends that he slept with some nasty girl... on top of that it happened on my birthday which he never called.. well he did but at 12 o clock at night when the day is over. i found out all the details and confronted him about it and of course he denied denied denied... how i know is that he told people about it and word got around... what makes this situation even more messed up is that i most likely got hpv from him and his extra curricular activities because before the trip i never had it.. it was months after this trip. i know what he did and so does he,, he just cant man up and admit it. i just feel really hurt and betrayed any advice to help me feel better about dumping his ***??