Find a reference!
General proportion stuff: head too big, shoulders too wide, hips too narrow, legs too long, arms too short, crotch too wide.
Definitely take mysterymeat's advice here and nix the boobs until you've got the ribcage figured out and especially the way the arms join to the chest as this plays heavily into the shape of the breasts. Your whole midsection is just a big cylinder, take a look at a reference there, it has a lot of dips and bulges. Same with the lower legs and the arms.
I'd recommend killing the outlines and the shading and breaking it down into basic shapes. Get a bunch of shades and then just block out each muscle group/major form. #1 tip for drawing the human body is there are ONLY convex lines.
EDIT: Legs too SHORT sorry, or more accurately legs out of proportion with torso.