What do you want for yourself? Where do you want this relationship to go?
Maybe you should talk to him about it, ask him where he thinks its going or something. Do you guys talk about seeing one another?
My biggest question: if you are unhappy in your marriage, why are you staying? You need to be happy with yourself and own your life, and sounds like confusion everywhere. Personally I would try to straighten out the home front FIRST-get a divorce or make it work, then decide on the other guy. But I would make it clear to him whats happening.
Sounds like you could be honest with the person youre talking to online with-with that-I would let him know how youre feeling. Like what you want with him, your intentions, feel him out with questions and then you'll know where he stands.
Goodluck
everything happens for a reason...beginning to wonder why.