Not sure what's going on. Ideas?

I'll try to keep this as to the point as I can.  I've had an irregular cycle as long as I can remember, but lately thing have been better. My last 2 cycles started on March 13 and April 13. Usually, my period comes heavy right away. I can usually tell about a day or two before it will start, but I've been feeling the lower abdominal pressure and sore boobs for about a week now.  Yesterday morning, I noticed a few very small, bright red clots while wiping, and I thought it was starting. There has been nothing since. Not even a tinge of pink. What would cause bleeding like that?