Very fit up to 16, become unfit after broke collarbone. from 17 got chest pain when excercising had ecg, echo, stress ecg, 24h ecg. now what? 22 year old

Start exercising: I assume from your question that none of the tests showed a serious problem. There are many ways to get fit (swimming, treadmill, stair-stepper/elliptical, bicycle, stationary cycle, walking, water exercise). Try to find an exercise that you can do but not bother you. It may be helpful to work with a physical therapist or rehabilitation doctor.