What Causes Prolonged Bleeding After An Abortion?

Before I got pregnant last year, I had irregular periods and I had them every other month. I had an abortion in the middle of december 2009 at 12 wks. I started birth control 5 days after the abortion, and also had unprotected sex the same day. I didnt take the birth control any longer than 2 weeks, and the clinic lady told me I was suppost to get my period around January 10th 2010. I was getting cramps before I was suppost to get my period, but it never came, and I started getting discharge. I continued to have cramps and discharge, but I dont really have cramps now but I have discharge. The discharge was dark brown and light brown, but now recently its been yellow a few times off and on. I continued to have unprotected sex a lot ever since the 5 days after the abortion, and he did cum in me. a little over a week ago I started bleeding but it only lasted two days, and by the next morning it was back to discharge. my periods always lasted at least 5-6 days.Am I pregnant?whats going on?