Okay this is my friend jumping my horse yesterday, we have been jumping forever, and i just started over fences with my horse...so critique what you can! I'll have more pictures of me in a couple days Thanks!
Your lower leg has swung back considerably, which has pitched you forward, as barn princess has mentioned. More work trotting in two point, and work with out stirrups will help anchor your leg underneath you and give you a secure foundation for your position in the air. Otherwise, your back is flat, you're looking up and you're using an appropriate release.
In this photo, your horse is not using himself correctly at all. He has not used his knee and shoulder to fold his forelegs, and is hanging his forelegs to an extent I consider dangerous. I would not be jumping him over single verticals without ground lines. He needs to be jumping a lot of grids and gymnastics with striding set for him until he learns to jump efficiently. Single fences need to have *clearly* defined ground lines until ....well, forever, unless the horse is being ridden at a level of competition that has a fence without a ground line or being ridden by an experienced rider who's confident of their "eye."