Personally, if my husband were cheating I would have to have a serious talk with him and separate for at least some period of time. That's just what I would do. A relationship is built off trust, and that would just destroy my trust in him.
But you asked for a spell. You could try a binding spell, I think. For the woman he has cheated with, or for him to make him not cheat on you anymore. You could make a spell which has the purpose of making him more truthful to you or more faithful. Any spell you can think of you can pretty much create. If you are looking for a more specific spell you could check under the spells tab and sew what there is there.
Personally though, I don't believe in using spells for love. It is an attempt on another's free will, is dishonest unless you intend to tell them what you are doing, and it doesn't allow for communication about each persons feelings in the situation. Once again though, that's just me. Remember that there is some type of karma to come back for everything.