Can u trust your man after he cheats?

My boyfriend,and i have been dating for almost two years now,and we have a four month old baby together. In my last five months of my prag.. he was cheating on my i kinda know,but i did i found out the day i had my son,when the young lady came to the hospt.I still get mad at him tell this day about it,and he said if i don't stop getting on him about it he will leave me.It's like everything he does now i get on him about,and i'm trying to trust him,but it's hard.So i would like to know what can i do should i just leave him or should i try to trust him,and stop nagging....