Much like there are serial killers, there are serial cheaters. Your cheater may be one of those who go from relationship to relationship, never fully committing to any one of them. These cheaters are often charming. They often know what to say in order to get out of any kind of bind. One of the problems is although they say the right kind of things to you, and may be sincere when they do it, you can not believe them. You can not count on them meaning what they say when the crisis is over.
Living with such cheaters often consists of going from one crisis to another. The cycle of infidelity goes round and round like a merry-go-round. In order to stop this cycle, you will need to wake up and take steps to change things. Yes, change is scary. Many spouses do not change due to their fears related to insecurity and the unknown. They prefer dealing with the known problem of the cheating to the unknown problem of how to deal with commitment and developing intimacy.
Nothing in this Work is intended to replace common sense, legal, medical or other professional advice. If your situation warrants it, please seek competent professional counsel.