I would also really recommend getting a trainer. It's great that you hav the confidence to do all this, and your horse looks like fun to jump, but in order to really be a succesful rider and to get over the jumps in a safe way, you need a trainer.
In the first picture it's obvious that you are pinching with your knee and you heel and lower leg has swung back. It doesnt' seem like you have very much muscle in your lower leg and I would really recommend just taking the stirrups off your saddle and building that muscle.
In the second picture, you need to bring yoru shoulders back, and again stop the pinching with your knee.
In the third picture, I think you are pushing youself and the horse too far. Your position doesn't seem that secure to be jumping that height. Your foot is way too far into the stirrups, and you need to keep your heels down.
Like I have said, it's great that you are confident to be doing all this, but you should really step back and get yourself a trainer. If you plan on showing with this horse, you are not going to place well if you don't work on your form. I'm not trying to be rude, just explaining. Everyone needs lessons, there isn't one person out there who would not benefit from a couple lessons.