Well, without a physical examination and probably a few tests, it would be difficult to point out a single cause to your wrist pain. A few possibilities include arthritis, carpal tunnel syndrome, muscle sprain, ganglion cyst, bursitis, osteophytes, fractures, nerve impingement/ injuries, infections/ inflammations, avascular necrosis etc. It is true that tendonitis is generally worse during activity, but may not typically subside during relaxation. The presence of a swelling on flexing the wrist could correlate with a ganglion cyst, osteophytes formation etc. It would be best to get evaluated by an orthopedician for a conclusive diagnosis. An evaluation may include a complete physical examination and a few tests like routine blood tests, MRI etc. After a cause is diagnosed, it can be managed accordingly.
Hope this helps.
I am sorry you are going through so much. Have you seen a hand specialist?
If not you need to. A general doctor does not know enough about the hand/wrist. If you are near a teaching hospital I recommend finding a good hand surgeon there, if not here is a website to help you find a hand specialist--
I hope this helps and you get the care you need,