Advice from one who has been there: The pain will start to diminish about 24 hours after you kick him the heck out the door!!!!
One July my first husband started saying, "Wouldn't it be fun to be single again?" I was so dense that it took me a few more months to realize he was cheating. Believe it or not, I lived with him for about 16 months after I knew he was cheating. (STUPID!!!) We were members of this fundamentalist church at the time, which contributed to my stupidity.
All the while, he was manipulating me...saying things like "No one will ever love you like I do." I felt terrible...like such a loser. FINALLY, he left me, to move away to be with his sweetie out of state. After about 24-48 hours of tears, I realized that I felt GREAT!!!!!
Not surprisingly, his sweetie broke up with him about 3 months afterwards. He wanted to come back. He cried and begged to come back. By then I was empowered and knew how much better my life was without him. No way was I going to take him back. His leaving me was one of the best things that ever happened to me.
So, my advice is kick him out!!!!!