Is there a chance that I'm pregnant?

Usually I have my period around the 3rd day of my sugar pill week. I start getting cramps the day before and I know that it's coming. My last birth control pill before the sugar pills was on Thursday, so I expected for my period to be here by Sunday. But there were no cramps, no blood. On Monday I finally got something, but it was only brown blood and there wasn't very much of it. On Tuesday there was even less and there's been no red blood or flow of any kind. I know worrying about it won't do me much good but did anyone have this happen to them and later find out they were pregnant??