Most Helpful Guy
As much as it hurts, I kinda think that you're this guy's 2nd option, otherwise he wouldn't talk to you that sporadically and your conversations wouldn't be mostly sexual. If I were you, I'd stop talking to him or reverse his game and try to make him prove that he genuinely cares. In order to do that, you could ask him out or something like that. Let's see if he'll back out or not, because talking about marriage etc sounds way too farfetched.