My right ear is very itchy inside, dark brown gooey earwax that comes back within hours. left ear is perfectly fine. what could this be?

Too much: Earwax is not produced in noticeable quantity within a few hours. Thus your problem may be from large quantity of earwax which is bringing off slowly given the appearance of recurrence. On the other other, the dark gooey stuff may be from an infection at the external ear canal which may require a topical antibiotic or antifungal agent. Let your doctor take a look at that ear .