I'm not the right person to give advice for possible sex addiction but in my opinion, whatever the problem is, and if you really want to get help, you need to understand and find out why this is happening in the first place. And if you have trouble doing that on your own, then i think it would be best to go to a therapist that's right for you and talk about it with them. I personally believe that when we cheat, then it means that we're not 100% happy with our partner. Usually there's something missing. It's possible that you don't wanna believe that. If this is a case of an addiction things might be different, I'm not sure. I think you need to keep an open mind about it, and if you're willing to go deep and find out what your issue is exactly, you should be prepared that some things might be different from what you believe/think. Hope you figure this out.