Advice about my bf please??:(?

My boyfriend and his best friend went to the movies on new years night. They went with two other girls. One girl Haley, is dating someone and I know she didn't do anything. But the other girl Paige, ugh. She gets on facebook later and starts sending me messages about how her and my bf, preston held hands at the movies. I texted him about it and he says he didn't, but he has a reputation of cheating, and pagie has a rep. of lying, so idk. We've been fighting constantly since then. I really love him and I wan to to be with him but whats a relationship without trust? Please give me advice. Should I dump him or give him another chance? Would y'all consider this cheating??