Why do i keep urinating, when i didn't drink too many fluids today?

Must have fluids: You either have extra fluids in your body (seen as swelling) or taking water pills. If non of the above, then you either pass what you drank or 10-12 ounces whichever is more. This called the obligatory loss to get rid of chemical waste ( melted in water). If none of that, you need to be checked to rule out possibility of diabetes mellitus or diabetes insipidus i.e. Inappropriate losses