I've been having pain in my right wrist when weight bearing for long periods of time while doing gymnastics. what could be wrong with it?

Any trauma?: Any lumps, any injuries? May be a ganglion cyst. You need evaluation with xrays.

Undetermined: There are too many possibilities to let me answer with any certainty. It could just be tendonitis or a ligament strain. However, there are a number of conditions that can be diagnosed only with x-ray, physical examination and, sometimes, an mri. You should have an orthopedist or a hand surgeon check this out to be sure.