Need help overactive bladder problem?

i've had lots of UTI's and even when my urine test was free from UTI i still had frequent urination problems, i finished tkaing my 2nd round of a 10 day prescription of antibiotics and i'm taking ditropan to stop the frequent urge to pee, the ditropan isnt working. what problem do i have? and sometimes i dont have UTI but have the very frequent urination anyway and im 20yrs old. the ditropan and anitiotics dont seem to be stopping the frequent urination