I would wait. My ex bf of 4 yrs did that to me. He was good for a while, but of course when we started arguing a bit he took off and slept with her. Then tried to come back!

Trust in a relationship is key. The fact that he did that, he violated your trust. He may love you with all his heart but what about you? I would hold off on marrige for now and kind of take the wait it out and see approach. If u 2 are meant to be it will happen right?

Oh n maybe couples counseling? Dont know if either of u are open to that. Me n my ex did that (only for 1 month tho) but it helped (in that short month, lol$