Which one do I choose? (20 characters)?

My trainer lately is over-scheduled and my lessons are either being combined with others going on a trail ride with her other students or cut short since the lesson before went long. And I've been riding for three years. 1 year of that was with a different trainer who had health issues and I only had like one lesson a month, but still. I feel like I haven't improved given the amount of time I've been riding, I feel like I am not that good. I don't even have my basic position right. I still slump, and I try to work on it but it doesn't really work out. I told her that i wanted to fix my position but she said that she has seen trainers that have a worse position than me. I have owned a horse for the past year and a half (almost) he is a 5 year old horse. I probably wasn't ready for him since i wasn't comfortable cantering yet, and obviously he is young. I actually have pretty good balance. I can deal with all the baloney he pulls, which isn't too bad. He is just unresponsive, he sometimes bucks (normally small), or spooks, but I can stay on well. I feel like he hasn't improved a lot in the time I've owned him I mean he has improved a ton, but not enough. He is worse on the trail though he likes to trot down hills, and that is my greatest fear in horse back riding since I fell off my horse i sponsored and got a concussion and he moved the horse before i was ready to ride again. There is this other trainer that seems really good, she makes you have a solid position before you jump she seems really good. Im going to work for her this summer for lessons and see if I like her and I might switch. So is that a good idea, and should I have my current trainer train my horse to jump for me. After summer, when he is a little older, don't want to damage his joints. She trained an OTTB and two of her colts to jump all by herself, up to 4 feet or more. I think she is really good teaching horse, but I don't feel like shes teaching me that well. I mean i have learned a lot, but I'm still not that good after all this time. thanks for the help and advice :) sorry for the length.