If you're under 21 and haven't been sexually active for 3 years or more, the powers-that-be (ACOG) state that you don't necessarily need a pap smear. That said, some providers will do it anyway. Most providers can do a pap with a light period (they'd be able to swab the blood away and take a sample of cervical cells. If you're bleeding heavily, that can be a problem, though it sounds as if it's fairly light.