You left off a lot of details here, so we're kind of flying blind. That said, if this guy is so great, why is he cheating on his wife and family? Sure he treats you great, you are the mistress. He leaves his dirty laundry at home. I think you should write this one off as a great fling and break it off before you get more involved and a lot of hearts get broken. My dad had a mistress, perhaps like you. They had great times until it finally broke apart my parent's marriage. Then said mistress started talking about marriage and dad promptly dumped her.