Should I stay or walk?

My bf of 4 years is cheating on me. I know and have proof but he continues to lie to me and say that I am his only one. I want to give him the proof I have but it will incriminate me. I have a baby with him.... I have fallen out of love with him...but care 4 him bcuz he is my child's father....but I want to be with other guys now.... we use to b so much more.... I have no trust where he is concerned anymore... so should I stay or walk.....