Hi, alright so as a traininer, I don't think its bad starting a horse walk trot canter at the age of 2/3. I have a 3 year old now that is going wtc and started over 2 foot fences. She is doing fine. If the horse has just started grunting and pinning her ears it probly doesnt have to do with your weight but she is mad about being ridden or uncomfortable. Numerous things, another explination could be "she is a mare" . NOW, because I have been in your position before im half and half. Yes riding more horses is awesome, you develop a nack for being able to get on different horses and not be worried/uncomfortable. However, I had a coach that also did this to me and yes for the first few years it was good until I wanted to get eventing, so I bought my own horse, him and I did awesome I started eventing and still ocasionally rode a horse for her but not often. However, she wouldnt let me jump over 3 foot and I was wanting to move on. So I switched barns. I competed that horse up to 4 foot within a month a my new barn.
Basically what I am saying is riding other hroses are good, but you have to reach for your goals too and if she isnt helping you get there then switch. A change isnt always a bad thing.
Okay thank you! I agree completely one everything you say. And the horse always kicks out sideways during everything but a walk. She is always pinning her ears back, and the teacher PRAISES her after she does! She's like, "Dawhhh your so cute! Such a good girl!" I'm like what the heck!? I'm trying to reach my goal so by the time I graduate high school I'd be capable of showing and stuff. :)