I am a 30yo woman with regular 28 day cycles. My husband and I have both been tested with no problems found but have not successfully conceived in 10.5 years. Today I started spotting very dark and then had dark/big clots. I am not due for at least another week for my period. This has never happened before. I also have cramping and back pain.

How has your life been lately? Stress? Illness? What it sounds like is breakthrough bleeding. Not a sign of pregnancy sad to say, but a normal occasional event in a woman's cycle. Good luck.