In persons below age 35, the most common causes of epididymitis are chlamydia and, less commonly, gonorrhea. At your age, most cases are not due to any
STD. Prostatitis is not due to any
STD either.
Despite your age, you should have been tested for gonorrhea and chlamydia. Was that done? If so and the tests were negative, then you can be sure no STD is responsible for the epididymitis or other symptoms. If not tested, the treatments you had should work against the likely STDs.