Creative things are hard. Not because actually -doing- them is difficult per se, but getting past the "i don't know what I'm doing" phase (even when you do) is super-difficult.
It's easy to say "keep writing," and that's really the only correct answer to any sort of "how do I get better?" inquiry, though the part that hasn't been brought up yet is the fact that -it's going to suck- for a while -- not the stuff you actually write, that is, but the process of doing so. You'll write some songs, maybe get some feedback here or there, but it'll suck -- that is, you'll feel unsatisfied for a while.
It's a hard truth, but they key point here is that -it's normal-. It's all too easy to translate "this sucks" with "i'm doing something wrong," and it's the latter road that leads to defeatist land. It'll take a while to click, but once you come to realize that it's not wrong to suck or to have a sucky time, you'll get over the hump. Until then (and after then, really), "keep writing" is the thing to do.
I dunno if that helps, but it's what worked for my own goofy self so it's worth bringing up, maybe-hopefully. Assuming any of this makes sense. :P