Here's what I know:
(1) Most girls make little things mean more than they do, so your guy might not be asking you out because he doesn't want to put the relationship in hyper-speed mode.
(2) Guys get nervous too. If you just started dating, he might be worried that you will say no or that you are already going out with someone else that night and by asking you, it will create awkwardness between you.
(3) He might be dating more than one person. (This should not upset you because you are probably dating more than one person as well). He might think its better to not take anyone out that night.
(4) You might not be his "A" game right now. Don't despair, it doesn't mean you never will be, it just means you aren't now or you aren't yet. (And if you are honest with yourself, is he yours?)
(5)Some guys don't believe in Valentine's Day or think it's silly. If you are dating one of these guys and you aren't his actual girlfriend yet, he can get away with ignoring the holiday this year without getting into too much trouble.
(6) Cut him a break until you see what he ACTUALLY does next Saturday. He just might surprise you.