Hi Ginna!
I really admire your clean, clear direct approach to your lines. It's clear you're confident with your tools. You also have a strong grasp of proportion. What I think many of your figures lack is a strong sense of weight and form. Some of them seem to "float" on the page and don't have a unifying energy to the figure.
I think a helpful exercise to build that sense of energy in your figures would be to spend a few sessions not worrying about the specific contours of the body and just focus on capturing the lines of action of the mody as well as the limbs and joints. Don't worry about adding mass or outlines, just get the direction of energy in the body down on the page. When doing these exercises don't be afraid to exaggerate - you're not drawing the figure but instead its energy.
It is helpful to me to think of the body structurally - it is a structure that has to hold itself up under gravity. A stationary figure is always pushing against the earth to hold itself up - the energy of the figure is in how the weight of the body flows down into whatever parts/limbs are pressing against the ground.
Some of the other commenters have already provided good feedback about form. Hopefully combining that with a stronger sense of energy and weight will push you over your wall. :)
