what did the doctor's say. it all depends on whether its a muscular or bone problem or it could just be you have a bad back from overuse in gymnastics. either way. heat it and then do some stretches like rocking in a tuck (the thing you do after a bridge) and then a pike stretch where some one is pushing you down. if its your upper back the grap a pole straight out in front of you and hollow your back (it almost looks like a cat) so your bringing your shoulder blades away from each other. theres tons more i can give you (i broke my back last year) if you tell me what area of your back its in, but those are the basic things you can do. tell me if this helps!
Find a good chiro or sports doctor that looks at how the muscles interact with the spine. Honestly, you will have to let the fracture heal. While strengthening the musculature around that area on the spine is a good idea, it will only involve a lot of pain and possibly damaging or retarding recovery.
I have the same problem you do. I have a recurring fracture to L5 in my back that will never heal---it refractured in the same exact spot it fractured previously. I was told to take about 6 months off--do absoultely nothing and that doing so would help it to start healing. I also saw a sports physcial therapist, and they gave me some exercises to strengthen the muscles/ligaments/tendons that are around the area to help support it.
Like BlairBob said, I suggest seeing a sports doctor or physcial therapist to get some exercises to help you strengthen the area around it, but I would recommend taking the time needed to heal before beginning. The fracture should heal with rest--no bending or jerking movments. I was put in a back brace (the first time around) for 12 weeks, which kept me from bending, and i was also out of the gym (of course).