Question....
How old were you when you started at a cheer gym?
How I did it: I joined a junior cheerleading team and started off just doing basics. Then eventually I started learning back handsprings. It took me a very long time to get the technique right. I would never jump hard enough, and my arms would end up crumbling. Finally, after a few months I could do it by myself on a trampoline. It was a little scary at first, but then I became completely comfortable. Then I had to start doing them on the floor, which was very scary at first. Cheer tryouts came around in May, and did my back handspring. After I had done it, I thought my coach had spotted me. Then she told me she didn't, which means I did it all by myself. I am now working on roundoff back handsprings, and they are coming along quite nicely. All you have to do to get a back handspring is keep trying. Jump hard. Give it all your power. And swing your arms back. Good luck!