First of all, good for you for getting back into the great sport of horseback riding. :) These pictures are not easy to critique, as they are pretty dark and you're pretty small. But from going from what I CAN see, here's what I notice:
For jumps these small, you don't need to be nearly that low on your horse's neck. Think of keeping your shoulders back and staying up off your horse's neck. By keeping your bottom over the center of the saddle and just folding slightly forward at the hips, you will keep a much more balanced position.
Your stirrups look too long. I would shorten them about 2 holes to get to the correct length. Shortening them will help you keep your leg underneath you. Also remember to sink down into your heels over the jump; it will help keep your overall position nicely balanced.
Try to keep your bottom much closer to the saddle, not way up in the air as it is here. It will help your upper body come up to the proper position, not hunched up on your (so cute!) horse's neck. When your upper boy is in the correct position, it shouldn't be hunched (looking like a 'c') or arched (with a hollow between your shoulders and bottom), but perfectly flat.
Now,for the things I like about your riding:
You're looking up and ahead, not down at the jump, which is always a good thing.
Your crest release is nice, and it is perfectly acceptable for people just beginning to jump. Later on, though, you'll start to hear about the auto release, in which the elbow-to-bit line is uninterrupted, and your remain in an elasticized contact with the horse's mouth over the jump. But you don't have to worry about that for a while. :)
Your horse seems happy and enthusiastic, from what I can tell from the pictures. Is there any way you have someone that could take a video of you jumping, perhaps zooming in on you a bit so we could see you and your horse better? It would be very helpful in critiquing and helping you improve.
Anyways, you're doing well for a beginner, so kudos to you! Good luck!