When he is drunk, his inhibitions fly away and he will flatter you and seem to care in order to get some attention from you and (if he is surrounded by his friends) to give the impression of a real charmer. This is all of course an act. When he is sober his behaviour will revert back to the real him. I really would not bother with this guy. Any drunk bloke will flatter a woman (for obvious reasons).

Men are shy too. When we're drunk, our inhibitions are lowered, yes. But this can make us reveal things we've been thinking about for a long time. Did he say this to you after talking to you over drinks for a long time (good), or just shout something crude across the bar (bad)? If he was casual toward you when he sobered up, this could just be him being embarrassed about the fact that he'd revealed his true feelings to you. He may be generally confident, but is he confident in everything, or just some things? Men protect their feelings sometimes too!