Frequent urge to urinate, but only drops, burning sensation, sexually active. Reason for frequent and little urination?

I m a 21 year old male, 135 pounds, about 5 7 , and I have had hemoroid problems for a couple years now. One day I got the instant urge to pee, and when I did, only drops came out, and it tingled and burnt very bad. I was afraid to pee again, my next pee was less painful, but after that I would get the sudden feeling to go again, and the pain was strong again. I went to the hospital, they said it was nothing, and that night when I got a boner it hurt. So I went back and they said it s possible that I have prostitus, and gave me a prescription. A couple weeks went by and I felt fine, now the pain is back, and I had the most painful pee ever and clear stringy stuff came out as well as a couple drops of pee. I have a girlfriend and we re sexually active but she hasn t had any issues. What is this?!