You didn't say how old you are, but this is a perfect description of some of the symptoms indicative of prostatitis (frequent urge to urinate, occasional premature ejaculation.), which is quite common, especially among men age 35-50. Some of the other symptoms are pain in the prostate/genitals and sometimes painful ejaculation (there may even be blood in the semen.)
Prostatitis is an infection, usually bacterial, in the prostate gland, which causes it to become inflamed. It is not the same thing as BHP (enlarged prostate) or prostate cancer.
Even if you haven't experienced any of those other symptoms, I would strongly encourage you to see a doctor and ask specifically about prostatitis. I have chronic bacterial prostatitis, and it is a nasty thing to have, so take this seriously.
If you are diagnosed with prostatitis, your doctor will probably prescribe antibiotics and may discuss some dietary/lifestyle changes with you. (Some things to curtail/avoid include caffeine, alcohol--esp. beer, and acidic or spicy foods.) I you do have prostatitis, I'd encourage you to be very dilligent about following the treatment advice--you really don;t want this to become a chronic problem.
Or, maybe I'm completely wrong.