I think you're beating yourself up too much. Most of these photos are technically good, insofar as the lighting. I think in one, you could have used more DOF, but in all honesty, you know what you're doing on the technical side.
As far as the "creativity" aspect, I'd suggest buying or looking at some magazines, same as some above posters. I've shot some of my modeling shoots trying to emulate what others want, and to add my own twist as well.
Really, it takes practice. keep on shooting, your photos are not horrible, and I honestly think you're being too hard on yourself.
As for learning when to under/overexpose, if you are given the luxury of doing so, bracket a bit. And then look at the results in lightroom or whatever image editing program you have and go from there.



