I'm 80 I swear!!!

Supposedly I turned 14 yesterday but I feel like I turned 80! Since I started wearing the brace(over two years ago) I have lost all muscle in my back.  Now to do a push-up is not even possible.  I hurts to get in the position let alone to actually do one. My mom said that I can do one but I am just now doing it correctly, I know I am because my gym teacher showed me how.  It drives me insane because it really does hurt.  Lately my family and I have been traveling.  We are driving to all the places that we go, these places are both over five hours away.  My lower back is now starting to hurt when I sit for over an hour.  I think it is because I try to sleep in the car and have to bend my lower back to do so.  Because the brace does not really let me bend my back it starts hurting and does not stop for a long time.  These are just a few of the issues that have started happening since I started wearing a brace.  My guess is that soon I have more than i can even count, that is going to bother me until I get it off and hopefully have them stop.