The only very important advice right off of the top of my head: Do not ever tell yourself you suck. Neither should you use similar words, like "fail". You do not suck, and your drawing is not a failure. Nobody is instantly magically awesome at drawing/painting/etc, it takes a lot of hard work! And when people don't understand this, they are not worth your time. Even "better" artists have no right to say negative words like that to another artist who might be at a more novice skill level.
So in short; be more confident! It's okay, you don't need to be perfect!
Now with that out of the way, I think you should work more from references and use more shapes when you're sketching. The more worked out problems in the construction, the less problems later on/ You do seem to already have a good sense of proportion, and now all you have to do is push it to the next level. Gesture sketching and focusing more on construction will work wonders.
I've noticed you tend to draw things in the same pose. Try something new! If you like drawing animals, here is a gesture drawing tool for animals: http://www.pixelovely.com/tools/animalgesture.html
Very useful when you need reference images but don't know exactly where to look. You're coming along fine, so don't worry. Just work hard and enjoy what you do. =) Keep up the good work.