Hello,
The very first thing that comes to my mind on the basis of your posting is diabetes mellitus. This disease occurs due to a deficiency of insulin (formed in the pancreas for control of blood sugar levels) and usually manifests with symptoms of excessive thirst & frequent water intake, frequent & night-time urination and excessive hunger & frequent meals.
For this, you need to get your blood sugar levels checked twice (first in the morning after a 12-hour fasting and second 2-hours after taking 75g of glucose). Other conditions that may mimic your symptoms include infections (particularly urinary tract infections), drug-induced, an excessive loss of water & salt (due to excessive/drug-induced urination, profuse sweating, loose motions/vomiting), an enlarged prostate (causing bladder outflow problems), an insufficient functioning state of the heart, liver or kidney, or an anxiety state. Please consult your doctor for a thorough evaluation, appropriate tests and further advice.
I hope it helps. Take care and regards.
Do you worry alot? Under a lot of stress in the last 5 months? I know it sounds crazy but anxiety and stress can cause your bladder to go crazy. Your bladder is full of nerves so if you have been constantly worrying about this sensation and that the Dr.s arent finding anything... you could be making it worse. I've been there and once all the tests ruled everything else out I finally accepted that it was anxiety. I got on anxiety meds, Lexapro to be exact and within a month when my nerves were under control the constant urge to urinate disappeared.