If stress was the cause behind my overactive bladder, would i still be urinating even if i hadn't drank any fluids?

Yes and No: Depends on how the words are interpreted. A person who needs to go pee more often than usual, and has psychological stress as part of his reason, will still have some stress and some need to go pee even if he drinks less fluids. It will help if he drinks less fluids, but in the end, he might still go to pee the same number of times, but of course have less quantity of urine per pee episode.