Need more answers..confuseddd...help?

So i have been going out with this kid for almost 2 years, and i just found out he was seeing another girl, even though it was only oncee. He kept it from me for about a month but only because he knew i would get hurt if i knew he hung out with another girl.. the girl is disgusting by the way..shes slept with half the town.. anyways, i also asked her and after my boyfriend admitted it to me well..their stories are really close but not exactly the same. She told me they had .. and trust me..she wouldnt lie about something like that because she would just tell u when she slept with someone.. and she said hee asked for it first. While his story was that he saw her locked out of her house n it was raining out n so he felt bad and brought her to his house.. when no one was home. i dont believe that, but its hard to believe he would even do something like that because hes always been so good to me and never done something like this..or at least not that i know of.. and he is on vacation right now and he feels reallyyy bad about bringing her to his house so i dont think he would do anything while on vaca.. and im going there too in about a week and he said he will do anything to get me back once im there but i dont know if i should give him antoher chance.. i dont even know if were broken up right now.. i think were just on a break, and i cant stop crying, its so hard. i love him more than anything nd i thought he did too but i dont know what to do.. should i stay with him and worry hes gonna do something like this again?? or leave him.. i am already heartbroken.. ill die if i ever see him with another girl... help me pleaseee