I've had a period for 15 years now and every period I've had is usually pretty heavy last 4 days maybe 5. Last month I was 3 days late and my period was very light. Only showed up when I wiped never was in my urine anything. Didn't have to wear pad or tampon also only lasted 3 days. This time around I'm 4 days late with 30 days between periods and my max is 27 days. The first day it was only when I wiped it was very light pink few hours later it quit and then today there was nothing. I went and got a blood test done today and it was negative. What else could it be?

The blood test was seen by your doctor right? Did you explain all of this to him?

We can't tell you here what it is. A diagnosis cannot be given on the internet.

Pregnancy, anemia, early menopause, stress, extreme exercise, short term disruption of hormones, changes in diet or drugs or supplements... on to more rare conditions. It just doesn't help to ask 'what could it be' when no one knows 1/100 of what is needed to know about you.