What Causes Prolonged Menstrual Bleeding?

i have been bleeding for 11 days it is regular flow and very dark on the pad, when i urinate however it is bright red when i wipe. Could this be happening because i took the morning after pill twice in one week and when i started bleeding i took birth control for a week? Or is this something else. I just gave birth 2 months ago and stopped bleeding exactly 6 weeks later, then started to bleed a week later for 11 days. I also suffered a uterine inversion and had surgery. What could it be causing this?