It's hard to see details in your picture, but I believe your stirrups may be too long. Without flexibility in your ankle, knee and hip, you must grip to stay with your horse and that makes it hard to soften your body to stay with the motion. Try raising your stirrups two holes, then lower your jump two holes and add three ground rails (spaced 4' apart, with the last one 9' from the base of the fence. Then trot in.
Pick up your two-point position as soon as you are straight on the line to the ground poles/fence and focus on letting your weight drop down the back of your legs into your heels. When your heel is deep, you can then close your legs ina firm squeeze from calf through thigh. You *do not* want more squeeze in your knees compared to the rest of your leg.
As you approach the ground rails, move your hands halfway up your horse's neck and press down into the muscle on either side of the crest, taking a handful of mane in one hand to help yourself keep your hands down and forward. Allow your upper body weight to rest there, with a flat back and your eyes up and looking ahead.
If your horse is likely to drift left or right, use some side rails to form a chute to the base of the fence.
Giving yourself time to settle into your position before the fence will help you get comfortable with it over the fence. Then your body will learn what it's like to go *with* the horse in the air, instead of being tense and dropping back into the saddle too early.
Repeat the trot in exercise over a low fence until you are comfortable adjusting and maintaining your "new" position. Then add another small vertical 19' beyond the first for a one-stride canter out (and stay in your two point for at least five more strides after the fence to encourage your body to really learn the balance of that position). After you can do this exercise without thinking about it, you should be fine to begin cantering small fences. Start by doing the same thing... prepare your jumping position several strides out, so you can just wait for the jump to come to you. In the early stages of learning an effective, stylish jumping position, waiting until you are right in front of the fence to prepare and execute is just too little time. There's too much to remember and do close up!
The rider in the second pic has a good upper body/head position, but her stirrups are also too long and her hands are too high on the horse's neck for effective style. Her hands are, however, in the correct position in terms of how far up the neck they are reaching. Compare them to your own position in your photo. With your hands so close to the withers, it's very hard for you to allow your upper body to close forward with the motion of the jump. Too-long stirrups just compound your hand problem.