Urine difficult n frequently urine.

I have urine start problem and frequently urine also. i done all testers but not found any problem, left & right kidney normal. Urinary Bladder is adequately distended. Urinary Bladder wall show normal thinkness. No mass or calculus is seen. Prostate is normal in size & show normal echo texture. urine examination and culture is normal. no pyogenic organism grown after 48 hours of aerobic incubation. But i have problems of urine start urination (1-2 mins to start) (feel like some thing to stop to passing urine) and frequently urination that last 2-3 months. Medicine but not improvement flodart 0.4 for 15 days, alfoo for 5 days. Please Give me bestest medicine for that problem bcoz my exams is coming. i dont concentration.