Hello, and I hope I can help you today.
When your period is late, the blood and tissue that normally is passed with
menstruation has longer to build up within your uterus, which usualy will give you a heavier, crampier period.
Secondly, the substances that your body secretes during menstruation to make your uterus contract, called
prostaglandins, also accumulate to a higher level. Prostaglandins have the side effect of making your intestines contract as well, and many women experience
diarrhea during a heavy and painful period for that reason.
So there is no reason to suspect that these symptoms are due to
pregnancy if your pregnancy test is negative, as they are typical for a delayed menstrual cycle.
To help reduce the cramping and diarrhea, taking an anti-inflammatory pain reliever like aspirin,
ibuprofen or naproxen will reduce prostaglandin release and ease these symptoms for you.
I hope I was able to adequately answer your question today and that my advice was helpful.
Best wishes,
Dr. Brown