What Causes Frequent Urination While Blood And Urine Test Were Normal?

I have a frequent urination problem for about 4 month I need to urinate more often than usual after every 30 min i have done all urine, blood test but all 100% clear and the condition going worst every doctor gave me so many medicine but these are useless i have took saw palmetto 450mg after using paining on penis left side and bladder left some side its on right side.