First, stop playing blitz. You meed to play longer time controls. Some people just aren't very good at blitz. I'm almost 1600 rated OTB and have trouble getting above 1300 in blitz.
Without looking over your games, you need to make sure you are following opening principle. Do not leave pieces unprotected. Make sure you know some of the basic checkmates and work on tactics.
I'm bad, like REALLY bad. It got so that I tried the chesskids site and I got whooped repeatedly by qwerty, the 400 rating robot. This after losing over and over again on this site.
So no kidding, all joking aside, maybe the kid site is where I need to be? I know its for kids and not adults, but other than that, the lessons there seem to make more sense to me, and the site seems better organized. I was thinking about getting a premium account, and that one is cheaper there too.
I know they don't want adults over on the kids site, this was more of a commentary on how good the kids site is, and also a solicitation for advice on where to start on this site for someone who knows the rules of chess and how the pieces move, and that's about it.