My ear was hurting badly for 2 days so i went to an ent doctor and he prescribed me antibiotics.now after having antibiotics for 3 days,my ear is draining but no pain or fever,slightly itching.what could be the reason and what should i do?

You were likely to have severe earache by a bulging ear drum by the accumulation of fluid associated with inner ear infection or to have a large blister over ear drum. It seems ear drum got perforated resulting in drainage of fluid accumulated. Use shower cap to prevent water flowing into an affected ear while taking shower and continue to take antibiotics prescribed.