Lol I was in a similar situation and I ended up learning he fantasied about me too. We also got into a relationship for a while but that's history.
Well, it's usually hard to stop these thoughts imo. But you might just have to try your best to ignore then and force yourself to look him in a platonic manner.
Or...you could go for it, take a chance. You never know, he may be thinking about you like that too.