When I look at these I feel like you are "chicken scratching" which means, drawing very short lines to amount to one long line. And these kinds of lines often look very wobbly, not very flowy, and the energy of the pose leaks out from them. What you can practise is doing the poses wiht as few lines as possible, Maybe give yourself even less time than you have before, to force yourself to make stickfigures and capture JUST the pose and no needles details.
The point of gesture drawing isn't to perfectly capture the model, it's to capture how theyre posed, its a good thing to exaggerate, you learn a lot by just experimenting with exaggeration.
here are some examples of what I mean
Keep practising and you'll get there : ) just think about your lines more
heres a guy with more tips: https://www.youtube.com/user/Sycra
hope it helps : D