Wow, Prismacolors ROCK! I have all Prismacolor colored pencils, I think 24 colors? All water colors of course, but that was a pretty penny too!
I think you're one of the few that can pull off a marker drawing without filling the pictures in completely. Your style is amazing dude.
For tips on the female body:

Though her face is a little messed up, her body has plenty of curve and if you look close enough she is put into a rather uncomfortable position, but because of the flow of the drawing it look natural.
It's important to remember that there is no square shapes within the female body, even a girls hips are just a large circle. If you can imagine drawing a bunch of balls balancing on each other stacked within the the female form you'll be able to go far.
What's really amazing is that the female form (females in generally amazing) is that it's actually typically harder to draw the female form, so don't be surprised that it's taken you this long to do it, or why it's so frustrating.
Use shapes at first, the hips are larger than the torso, the head/jaw is curved, there should be no point (if there is it should be at the tip of the chin) what also help is to have no defined jaw line. Just a basic "U" shape will make your character look more feminine. A square jaw will make your character look like a dude with a females body.
Breasts, though it's a sensitive topic to many it is important to know a few facts when drawing an adult (possibly busty) female.
When a woman stands with no bra, her breasts will have "sag" (such an ugly word...) but think of a water balloon being held onto by the mouth, cup your hand around it and lift it up and the "sag" will go away, that's how a bra works. It cups the breast up to make them look "fuller" and of course, support.
If you are drawing a character without a bra, her breasts should not be touching, only in really tight bra's or chest pieces will their breasts look like the classic: "really-nice-cleavage"

The picture above is an example of "really-nice-cleavage" drawn by myself...
My male figure (this is an older picture) is done with all squares, can you see the shape difference from the male and female?

If you have any more question feel free to ask. I tried spewing everything I know about drawing and all the hints I learned from other artists.
ARTISTS RULE!!!