Oh, I'm so sorry you have to sell your pony, but try and think of it as a good thing--your pony will go on to teach someone like he/she taught you, and you can move on to a horse that will progress your riding. :) It's tough though, so I hope you aren't too sad :(
I am a coach/trainer myself, so I've seen this in different students. Sometimes, your body and how it's built (meaning torso/leg length) can affect how you ride a horse/pony (the balance of each can enhance or de-enhance your position/ability).
Hope it helps! And I understand about you not having a horse to jump. Hopefully you will find something that can help you soon :)