Im so sorry Booo. I do understand what you are going through to a certain extent. My husband had an affair (lasted months) when he was actively using drugs, drinking the whole bit. We were not living together at the time, but not officially apart if that makes sense.... I found out through a friend who thought I should know he had moved a girlfriend in with him.
Its a horrible pain, and I don't think you can do much but feel it. Feel all the feelings, ask all the questions, give yourself time to sort it all out. There was anger, hurt, fear, insecurities, pain, and lots of crying. I also never thought my husband would cheat, or have a long standing affair because we were best friends, connected at the soul is what I always believed.
He too was very remorseful and has done everything he can to be forgiven, make amends, prove his love. Marriage counseling helped us the most so consider it when some of the feelings tone down a bit. It gave me a lot of insight into my husbands emotional state, as well as his state of mind during the time of his addiction. He felt abandoned and alone, insecure, and tried to fix himself with someone else who told him he was wonderful, and didn't care about the drugs (because she used too). Anyway, I know in our case it was the drugs... that caused him to cheat, and we have worked through it now and the relationship is stronger for all the work.
Im so sorry for what your going through. Please take care of yourself, don't deny your feelings. Talk to your friends or family who are close because you need to have people to lean on. I would also suggest private therapy as an outlet - helped me tremendously. I think only time will direct your next steps.