I've recently had 3 miscarriages. my last pregnancy i had low progesterone. this pregnancy i dont. if i take prog pills bc history will it be harmful?

Unlikely: Progesterone supplementation is almost never harmful - although if it isn't necessary or helpful i recommend against it. Have you talked with your doctor about this? Have you been evaluated for recurrent miscarriage? Progesterone is only one of several possible causes. As a footnote, for women who need progesterone, taking it orally doesn't give adequate replacement.