Back protector blues, what should I do?

I had to get a back protector about 3 months after I started riding, so I could start going hacks. Normally, I didn't wear it when i was doing flatwork or jumping, only whilst leaving the arena. Somehow, my parents suddenly had a flurry of worry and I was soon wearing it whenever I was on a horse. Of course, I've been through many body protectors since then but they're just so uncomfortable!!! I have managed to persuade my parents to let me not wear it doing flatwork, but jumping and hacking still mean i have to wear it. It's just so restrictive and it's unbelievably warm! it's now summer, and I feel i can't hack out or do jumping because i'll just overheat and wearing it, i'm as stiff as a board. What age do I have to be that I make the decision not to wear it? and are there any tips or something to help me with this?