You are arming the ball. The clue is in your picture. Your offhand is not pulling across your body because it should already be across on contact. So you are late, arming the ball and not getting your weight back into the court. All things most of us have dealt with and still deal with at times.
I'd forget about your right arm and focus on the footwork and weight transfer. The right hand is the least important part of what you should fix IMO.
Please help TT Member BruceD get a wheelchair so he can play tennis again - http://tt.tennis-warehouse.com/showthread.php?t=496820