Broke wrist several years ago. sometimes wrist is so weak other times its ok. hurts to brush hair, carry tray at work, hurts to support weight?

Often pain gives the: Feeling of weakness . If this is so there may be a subtle difference that is causing the radius and ulna to be out of alignment so to speak or the ulna is prominent or the radius is tilted resultinginodcarpal joint pain. For this issue i'd start with your previous treating provider who has your old x-rays. Sometimes if a person has discomfort comparison views with the normal side may be helpful.

Malunion: The fracture may have healed in a malunited position altering the biomechanics of the wrist. I think an evaluation and x-rays by a hand surgeon might be necessary. There are subtle measurements that we look at at the wrist and correcting this earlier rather than later may prevent arthritis for you.

Needs attention : At your young age this is not ok it would be best to have this evaluated by an orthopedic surgeon a good physical exam and xrays may lead to an answer best of luck.