At three months postpartum with my 2nd baby i had midcycle bleed. went for transvaginal ultrasound to check on a uterine polyp i had and it was gone. i did start working out heavy again to lose weight could that have been the cause of midcycle bleed?

Working out could be a factor, but at only three months postpartum your cycles may still be a little unpredictable. Whether or not you are breast feeding and what you are using for birth control are also potential factors. Unless it is particularly painful or heavy it is not an immediate concern and should be investigated further if it continues to happen with future cycles.