The good news is you are not married to him. Now is the time to decide if you can fully forgive and move on. If you decide to stay with him then at some point you will have to trust him. But you have decide what your motives for staying with someone that cheated on you for six months are. For me, part of it would depend on his reasoning and how I found out. But he also needs to prove he is trustworthy. Those who have nothing to hide, hide nothing.

Good luck.