Miscarriage?

I am on CD 20 right now, and have been spotting lightly the past 3 days, then tonight it became heavy, with several clots and some abdominal cramps. .... All I can think is that this was a very early miscarriage. ... had anyone experienced this or know what it could be? ?? I emailed my Dr. To see what to do, but I am freaking out right now. .....