Possible Miscarraige?? Please Help?

Ok first off sorry for the graphic details but this is what is going on: I have been on birth control now for several years (same pill, have not sswitched brands) and my period has always been like clockwork. I have taken it every day at the same time (part of my routine :) and have not missed any pills. I am halfway through my current pack. Anyway yesterday when I woke up and went to the restroom I had quite a bit of red blood and period like cramping and that continued throughout the day. When I woke up this morning and went to the restroom there was more blood but it was darker in color and had alot of mucus clumps in it. Could this be a sign of a miscarriage or something else. I am begining to get worried, any help would be greatly appreciated. Thank you.