If that is the road you are going to take, don't ambush him with it but set a time to talk about it and have a very strict time limit for how long you will discuss it and then stop.
It will be hard and painful. When ex first cheated right after we got married, we never worked through this stuff. I know it needs to be addressed.
Just remember this wasn't him necessarily seeing her as better but easier. Perhaps easier to talk to, easier to get away with being "bad", easier to accept his horrible hours. Again this is all of his stuff, his problems. Probably didn't have a whole lot to do with you.
Just saying. kat
Me-53(and learning!) S24, S21, D18, D17 Just keep swimming, Just keep swimming. Dory