Today I started my period; it was 7 days late and had an abnormally light one last month?

The blood is not like it usually is. It is usually light, and bright red. Today it is very dark red, and think (mucus like). The cramps are even weird, they are usually mild and seem to be horizontal along my lower abdomen, and now they are running vertical from upper to lower on the right side, and it is up there with the worst pain of my life. I am sexually active, I was just wondering if it is a possibility that I am pregnant. I know it is possible, but I am just wondering what it seems like to someone who may know. thank you