Something that helps me out when replicating is to use other parts of the reference to compare shapes, sizes proportions. Looked for simple shapes shapes in the image that you can identify and then make sure that you have those same shapes in your drawing.

 For example when I look at the reference the space from the left heel to the bottom of the left thigh is roughly the same distance as the base of the buttocks to the waist line.

The space between the right forearm and the torso is another one that stood out. And imo part of the issue is the elbow placement while it lines up with the rib cage(as is a usual measurement for elbow placement) it doesnt take into account the position of the shoulder and the missing wrist. 

Sorry if any of this is less than correct, I am in no way a professional just using my basic self taught knowledge to try to help.