It would be important to know if he is looking for a relationship and if you only communicate via the internet or you also see each other.
There is nothing specific you ought to be doing for him to become interested in you. Afterall, if he is to become interested, it has to be in you the way you are.
He may just want a friend and someone to talk to. If this pattern you've described had been going on for a while, and he had not made any indication that he wants more of the friendship, most likely he does not. That does not mean that he does not like talking to you but you've got to make sure that he's not taking advantage of you. He should not unload all of his problems onto you.