Power clean:
You need to place at least another 45 lb. weight plate beneath each side of the barbell for your start: the barbell should be touching higher on your shins, probably another 2 inches higher. Place 45 pounders on the barbell on the floor as if you're going to lift, see where the barbell touches you on the shins, then stack enough plates underneath it for your work weight so that it touches roughly the same place.
Okay, now for your technique. Stomp your feet harder after you finish the jump. Slam your elbows up toward the ceiling aggressively for the rack. Do those two things, and you'll be doing much better.
You're also catching the barbell in the rack position with your hips thrust forward instead of with your hips more or less plumb with your midfoot and shoulders, like the picture on the right: http://www.crossfit.com/mt-archive2/PPIssues1.jpg
Back squat:
Actually these aren't terrible, confuzzled. Some good hip drive here, but on the last couple of reps or so you're borderline shooting your hips, so you've got to fight like hell to squeeze your chest "UP, UP, UP!" as you start getting tired.
All around, not a bad job on either of your lifts, especially with the power clean, which you've only just started to learn, and especially considering that you've been learning them all by yourself. But you've got to practice the power cleans a lot more, and since the weight isn't all that heavy for you yet, you can probably get away with practicing them two times a week until you feel more confident at them.
Oh yeah, and gain some weight, NOW!!!.
-Stacey