On friday i was carryig boxes and my wrist started to hurt a lot. i've had a wrist brace on for 3 days now and it's the same. how long to heal?

Sprains: Sprains take a few weeks to heal especially if you are still lifting. If there was no dangerous injury you may not need X rays. If pain persists by the end of 1 week an X ray may be helpful to confirm that no bones were damaged. If still persisting a better test such as an Mri may be indicated. Keep using the splint, rest it, take over the counter pain meds and see what happens.