Well, without a clinical evaluation it would be difficult to comment on the situation for sure. If your doctor feels its RSI, it is likely that he/ she is correct. I would assume there has been a complete evaluation done by your doctor (physical examination and investigational studies) to rule out other possibilities such as inflammations, degenerations, neurological issues, micronutrient deficiencies etc; that could present similarly. I would suggest following the management plan suggested by your doctor for a while (which may include rest, physiotherapy, anti-inflammatory medications etc); and see if it seems to help. If you do not see any improvement, you may consider a second opinion from another orthopedician.
Hope this helps.