Is he cheating on me.?

ohhkay so one day me and my boyfriend were walking together to class and this girl comes out of no where and she takes him away from me and she starts yelling at him saying why is he cheating on her cousin and he says no. and so ijust left with my friend to class. and iwas crying obviously. and then i was talking to his best friend and his best friend was saying that it was maybe a girl that likes him and wants to seperate us and a couple of people were agreeing. but then the class ended and my boy friend comes up to me and he says ey lets talk and i go no. and push him away (i felt mean). and then i went to class and i was talking to other people and some people were saying hes a cheat he cheats on a lot of girls. and this gurl said hes not like that. so then we all left and i saw him again and he said i think we should talk and we did and i asked him and he said no he said that the girl thot he was still going out with her cousin but they wernt and blah blah. and he says he isnt cheating on me. but idont know if i shoud beleve him or the people who say he is. so can anyone tell me with this information if he is or if hes not. ??