Last week I was in a car accident, and the air bag inflated and hit me in the chest pretty hard. I have bruises on my chest, but haven t had any medical attention. I just shook it off, and felt like the bruised feeling would eventually go away. My sternum feels pretty bruised, and it hurts if I cough or sneeze. But I don t have any trouble breathing or anything. I have noticed a lot of blood in my stool since then, though. Today I went and I thought I had started my period because there was just so much blood. It s bright red. I don t feel uncomfortable or have any pain in my rectal area, and I haven t been constipated. Should I be concerned?