Look up, bring your legs more under you. There should be a straight line from ear, shoulder, hip, heel. Your shoulders need to be brought back and sit up a little straighter. I love the straight line from your elbow to the bit.
You may want to drive the horse more forward and lengthen your rein or arm a bit: notice the broken line of the neck (how it "breaks" into an upside down V shape) and hollowed back.
I might be wrong but your saddle may be too forward? Don't take my word for it..
“Have fun - Stay on top.”
"There's nothing like sixteen hands between your legs"