Burning in Urethra, for a year now.

Ever since I was young I'd get UTIs, but they'd go away or I'd take antibiotics for them. About a year ago I got one, and figured it'd go away after a while and to just drink more water, but it didn't. It kept going for months! It actually brought me to tears. Once I slowed down on water because my symptoms lessened it came right back. I was tested and there was no infection. No bacteria. I finally saw a urologist months later, and they couldn't find anything either. Just told me to stop drinking pop. So I did. And now its coming back.

Unless I drink at least a cup of water every few hours, and go to the bathroom every 2-3 hours, the pain and burning will come back. It is not possible to always do that, I have to wait at my job for 3-4 hours before a bathroom break. And I can't drink anything. Work is becoming unbareable. The weird thing is that when I wake up in the morning, from holding my urine all night, I don't hurt. I don't know what to do anymore.