Why is he sending me mixed messages?

[SomeGirly]

Okay so I have a crush on this guy. Last week he was super nice to me and he's smile at me, and say really nice things to me (In person and on FaceBook) and he would always glance at me and smile, and even make me feel better when I was down.This week he hasn't been talking to me, though he has still been looking at me. Like it's weird how just a week ago he was being friendly and this week he was being moody? Tomorrow I'm hanging out with a group of friends and he's going to be there. Why is he sending me mixed signals and what should I do? Thanks in advance!

[why]

sometimes when a guy or girl does this, its because they feel they have expressed their attraction but didnt feel as though the other person expressed it back, and kind of want to cover their tracks or hold back a little until the other person shows encouragement.