Urge to urinate after drinking water.

As soon as I drink some water, it becomes urine within half an hour and I feel the urge to go to bathroom very often. I feel like body is not absorbing the water much and going to straight into bladder and I feel pain due to frequent urination. this problem becomes severe when I masturbate or have sex. I also feel some itching and moisture near that area sometimes even though I keep it clean. earlier when I went to hospital due to this problem, there was minor UTI in the test report and doctor prescribed antibiotics. now I am not sure if it is the same problem this time or something else. if it is the same, I want to know why it keeps happening and what can I do to prevent it. Thanks in advance for helping me to clear my doubts.