I just stumbled across this situation. Testicular pain has a wider "rule-out" diagnostic set than "blue balls" and "testicular torsion" (very rare).
The primary care diagnostic alternatives should inclde primarily epididymitis, an inflammation of the ducts that lead gland substances to the urethra. The two common causes of epididymitis are infection and idiopathic (a nice way of saying unexplained; what "blue balls" might be called). After your primary care does a urine culture, if it's positive you treat the infection, if negative, you take aspirin or a non-steroidal anti-inflammatory like ibuprofen. Only if that doesn't work or if it re-occurs do you need to see a urologist.
If the dancebelt wear is causing congestion in the different ducts that supply the basis of semen (and idiopathic epididymitis), it's probably too tight and you may need to not pull it up to tight or to wear some padding.
Your primary care doc should have logged onto the US National Library of Medicine to search on this problem to understand the needs of the male dancer. But all too often docs don't have time to study every problem in detail, and the history of dancemedicine is disappointing (the move to start a dancemedicine specialty started in the early 1980's and didn't get very far, and sportsmedicine docs (we called them jock-sniffers back then) were never interested in dancers, especially male dancers).
balletboy[/i]