Your symptoms like feeling hungry and frequent urination
constitute Diabetes Mellitus
. Weight can not be gained permanently by just drinking water. you should drink enough water needed to your body.
I advise you to visit doctor and get your blood checked for glucose. Further urinary tract infection
and thyroid profile should be evaluated. Thyroid dysfunction
can change your eating habits and weight, moreover it can also effect your menstrual cycle. Once diagnosis is made with help of lab test then it would be easier to treat specific disease.
Hope it helps!