I agree with kaykat31 you have a lovely flat back, but your lower leg has slid back. If you work on pressing your heels down that should help shift your leg forward and keep you from clamping with your knees.
Where I disagree with kaykat31 and Azures is your release. Yes, your fingers need to be more closed (just in case your horse slips on the other side of the jump, you don't want your reins yanked out of your hands). BUT what you are doing is an automatic release. I detest the way crest releases are being taught and done now, especially when the rider is laying all over the horses neck. A good automatic release gives the horse a chance to stretch out over the jump and use their head and neck to balance over the fence. Your hand could drop slightly (ideally you want a straight line from the horse's mouth, up the rein, and through the rider's wrist to the elbow).
Check out this article about releases: Horse jumping release: The crest and automatic release in jumping
Personally, I would have you continue with the automatic release and work on exercises that improve your leg, balance and core strength. You've got the automatic release, why back-track to the crest release (and risk becoming dependent like so many neck-laying hunter riders have become) when you can simply focus on improving your leg position. Especially for this height of fence :)