I am very sorry to hear that.
I will admit that I agree with porrlittlefish. You seemed to seek support while staying with him, so I did not get into the 101 reasons why you should toss him, but give me permission and I will

is that on your mind? or are going to stick it out with him no matter what?
Its a tough spot, one I cant help but not understand fully from either side, one thing I have found is that unfaithfulness is not a situational "thing", its a moral "thing".
I hope you find the strength to deal with this what ever the outcome.