Yeah now that I think about it I see what you mean. I've been trying to study anatomy a bit more which will probably help. I think my weakest areas as pointed out by others on this thread seem to be the legs and the hips. I should also work on other areas, but this seem to be the thing I should work on the most. Also, finding references for this pose was actually kind of a pain, so I tried to improvise which didn't really work out.
I also probably should have followed a simple piece of advice, which is to try the pose myself before actually drawing it. I didn't do it as much as I should have.
Thanks for your advice!