How to forget? forgive? please, this is long but i need help :/?

Why do you want to forget about what you have seen? What you saw will be what will save you. You break up with him. Now. Don't be foolish and stay with him. If he's "playing the field" now, what's gonna happen later on down the road? What's gonna happen the next time you go to work and he's at home? The relationship will be unfair to both people because you might be bothering him every second of the day to see what he is doing because of a broken trust and he could be doing god knows what. You are definitely better off leaving him and starting fresh. I don't want to judge you but if you still feel that you want to stay with him, you clearly need help. Get out of this ridiculous relationship now before any other damage is done.