1st pic- Hard to say, but it looks like your pinching a bit with your knee and your leg has slipped back a tad. Otherwise it looks very nice.
2nd pic-Not much to critique here, I do love how you are out of her mouth.
3rd pic-I would rather see your butt in the saddle, but your back is nice and your chin is up.
4th pic-Cute! I wish I could braid like that...
5th pic-Looks to me like you have a tendency to pinch with your knee and let your leg slip back. I would say work on some stirrupless riding over cavalettis and poles, that oughta fix your issues.
6th pic-Good release, and your chin is up! Your horse has good form, knees nice and tucked. However, your leg has slipped and your knee is pinching.
7th pic-I love your horse! And you always have your chin up, a big plus. I sound like a broken record, but your pinching a bit with your knees again.
8th pic-Your back and chin are excellent, your horse is hanging just a tad, and your leg has slipped back.
9th pic-Not a whole lot to critique. Your chin is up very nicely though.
10th pic-Pretty! YOur horse is in good form, your chin is ap and back flat. Your leg isn't bad, not perfect, though.
11th pic-Your position looks perfect. This looks like the typical lazy pony, but your keeping up pretty well.
12th pic-Hard to critique, you look alright besides being slightly behind and not releasing enough.
13th pic-You're caught behind and in his mouth.
14th pic-Yeah... I don't need to explain
You have a very nice horse, just need to work on your legs a bit and you'll be great!