Hi, the symptoms you describe, especially painful urination is going to be rare that it should be due to masturbation, Slight chanced are however possible , but its really rare. However, the commonest cause of burning urination is usually infections. Its worth knowing if you have been exposed lately to any unprotected sexual contact. Other rhumatologic diseases could cause a syndrome of urethritis, joint pain. but to come to this conclusion, an infectious screen needs to be done with appropriate urethral swabs , urine cultures and sensitivity tests. Consult your family physician for help and get appropriate and timely treatment to avoid any complications. Thanks and best regards, Luchuo, MD.