moonlantern,
Welcome to the forum!
It’s great to see you finally post your work, and it looks like you’ve got a great start! 
There are some really beautiful aspects to this drawing, and your linework is one of them. You also have a very nice touch, and I appreciate that you’ve really brought out the subtle patterns and undulations of the skin through shading without compromising the main shape of things ~ for example, in her right leg. I think your appreciation of using Opposing Curves to create form, whether conscious or not, is really wonderful, and the only area where I think you’re getting lost is around the head and a bit around the upper arms.
Drawing in this direct way with a difficult to erase medium can be stressful, and I think that part of the way to alleviate some of this stress is to lightly lay in the complete figure with, say, a sharp 4B (relatively soft) pencil before going in to really render with the fine gradations of charcoal. It is difficult to simultaneously concentrate on expression and basic proportions at the same time, so it makes sense to separate the two processes.
There are, of course, many benefits from just drawing directly onto the page ~ you learn to trust your instincts, to take risks, and to learn how to fail and learn from your mistakes. (By no means do I think that you have made major ‘mistakes’ in this drawing). I think of drawing itself as an act over time ~ you do a lot of drawings, and it’s all a process of learning how to ‘draw’. So it’s not always useful to fret over single drawings…the goal is to do many, and to improve how you see.
I think also if you have not already done so in school, that you would greatly benefit from doing Master Copies of Drawings, Paintings, or Sculptures by Renaissance artists like Michelangelo, Raphael, DaVinci, and later artists like Rubens.
Great work so far, and I look forward to seeing how this turns out! Please post your updates, as many as you feel necessary. 
Cheers! 
~Rebeccak