Is Chronic Epididymitis sexually transmitted without STI's?

[nazxamari]

I am a 17 year old guy. On July 27th of 2015, I received oral sex from a guy I didn't know. Later that day, my scrotum had swollen up completely. I had no discharge or pain from urination. The next day I went to the clinic and got tested. My results were negative for everything. I figured that may have been too soon to detect whatever I may have been infected with, so I got tested again a week later. My results were all negative again. The only symptom that followed me was epididymitis. Its been about nine months since the incident and I am still suffering from it. I have been given Doxycycline and Ciproflaxin which have helped. But I have continued to masturbate and It gets worse every time I do so I'm withdrawing. I just want to know if its possible to develop Epididymitis from sex even though you might not have an STI? Maybe the guy had another type of oral bacteria that entered my body. A bacteria that is not Chlamydia or Gonorrhea related. It cant be a coincidence that I developed my symptom right after having oral sex but tested negative for everything. I know he caused it! I also want to know if the Doxycycline and Ciproflaxin would've cured Chlamydia and Gonorrhea if I did have it? Somebody please help me. What should I do? Should I get tested again? Should I quit masturbating for awhile?