There is much more involved in many cases of cheating than having sex with another person. There is an emotional side to cheating that can be equally, if not more, devastating to the person you've married.
Do you feel guilty about the chats you're having with the other woman? Do you enjoy the time you spend with the other girl but, in the back of free chat with girls your mind, feel that you're doing something wrong at the same time?
When you feel as though what you are doing is wrong; it's usually a good sign that it is - at least on some level. People don't generally feel guilty for no reason. It doesn't mean that you're a bad person or that you're trying to do something wrong but that feeling in the back of your mind is telling you that you should not allow this to continue. It's the first warning bell.