Like others have mentioned, I think you have used a lot of sketch lines, which make it hard to see the true shape of your figure. Marc Leone at the Drawing Database
https://www.youtube.com/channel/UCNPLX1hfy3Q8zr4eKvmhLGQ/videos always talks about thinking about the 3D form you are trying to create, break the body into common (cube, sphre, egg, pyramid) forms. That said, I work digitally sometimes too, and find that quick shading with the same size pen, especially if you do not have tilt sensitivity, results in a lot of thin lines. Sometimes, I thought your lines were to indicate shade more than form. You could try making your brush size larger for the shaded areas (really hard to do in 2 minutes!). Keep drawing though! You are giving me inspiration.