Problem while Urinating only at night time

Patient: Hi, am a 21 year old girl. From the past 20 days or so i am having a prob while urinating which happensonly when i get up in middle of the night to pass the urine. I feel an urgency to pass the urine, butwhen i try to urinate am unable to pass the urine completely, am getting only a few amount or sometimesnothing. This happens only during night, in the day time i feel completly normal. And there isno other problem to me other than this. I dont feel any pain while urinating. Usually I drink a lot of waterand i’l get up atleast 3 or 4 times during the night time to pass urine. But this problem has started recently whichwhich was’nt there before? I want to know what is the reason and what i should do? Please help me out.