My period stopped 3 days ago and today a big chunk of blood came out. why?

Common Issue: This is quite common. Small amounts of clot can accumulate in your uterus during menstruation, then suddenly pass later after you think you have finished. I sure way to prevent this is by getting on a birth control method like the pill. Aside from controlling your cycle and preventing pregnancy, there are some real health benefits to Pill use, like less chance of uterine and ovarian cancer.!