What Causes Vaginal Discharge After Completing Cycle?

6 days after my period ended (I have 30 day cycles on average), I began having vaginal discharges that had blood in them. It was light to moderate bleeding. I am sexually active and had unprotected sex on May 2, 5 and 9 (the first day the bleeding occurred). We had normal sex on 2nd and 5th and he ejaculated into his hand on the first time and we didn t finish on 5th. But on the 9th, we did anal (not doggy position) and he ejaculated inside me. I know it s strange but I m getting paranoid that I m pregnant. Could it be possible? Also, I read that obese women have a harder time getting pregnant. Is there any truth to this?