Frequency and urgency to urinate can be due to :(1) infection but your urine analysis ruled this out (2)prostatic problems such as enlargement or inflammation (3) cystitis
which is inflammation of the bladder, can occur in the absence of an infection (4) diabetes- high blood sugar can cause both of these symptoms (5) alcohol use (6) overactive bladder
(7)neurological disease (8) diuretic
medication (9) caffeine (10) anxiety
Your can consider re visiting your doctor who may request a urinary diary to assess how many times you actually go the bathroom and the amount of urine passed (the see if you are passing small amounts frequently or if there is an increase in your urinary output).
A repeat urine analysis may be done and possibly some blood tests.
I hope this helps