What should i do? i dont want to screw this up?

Theirs this guy I really like. ( hez a Senior, I'm a sopre) well 2 days ago I sent him a message on Facebook saying hey. What's up? He never responded back. He's in 1 of my cles, is single, from what I can tell isn't going after any girls. I have talked 2 him once or twice before. I don't want to come across as annoying, and I definitely don't want to make myself seem like a creep. Should I lay off and forget about him, or flirt & hope he gets the hint? Thanks in advance