Oh boy, alright, where to begin?
First off, read all 3 parts of Eric Cressey's "Mastering the Deadlift" series. It will be in the article archives; should be easy to find.
Next, ditch the cross trainers and pull barefoot (or in a flatter shoes such as Converse Chuck Taylors).
Also, when you put plates on the bar, the smooth side of the plates should be facing out.
Learn how to maintain a "neutral" spine position. Your low back should not have that weird hump; push that in and then pop your chest out a bit more.
Ditch the belt for now. You are a beginner and should not need it with such light weights. I'm sure your low back hurts while deadlifting, but fix your form and that will go away.
There really is no point in me listing anything else, because you need to fix just about everything. If you really want to get better at deadlifting, start reading up on it and watching videos of good deadlifters, and then practice with fairly light weights.
Here is another article and a few videos to get you started:
Sorry if this seems harsh; hope it helps.