He may not be cheating, I am married, member of some sexual accounts. At times I chat with men but I don't meet up with anyone. My husband knows I do this, we have been together for many decades, it is just a part of who I am. I will admit I didn't tell him for many years because I was concerned it would harm our relationship but it didn't. In fact I feel better for telling him. Your partner may not be meeting up with anyone, be sure you have proof he had sex outside your relationship before you address it, you don't want to spoil a good thing.