It sounds like you may have some piles, which will be made worse by your constipation. Please make sure you are drinking lots of fluids, remember you need loads extra as you are breastfeeding. Try not to strain on the toilet and go as soon as you have an urge (even if the twins would like fed first - holding it in makes constipation worse).

Have you had your 6 week post birth check-up yet? If not then mention this at your appointment, and if you have already had your check-up it would be worth your while making an appointment to get checked as bloody stools are sometimes a symptom of something else so should not be ignored.