I am 4 days late. negative hpt. one light red spot on tp. very mild very sporatic cramping. what could be the case?

Ovulation: The most common reason for a late or missed period (besides pregnancy) is a late or missed ovulation. This isn't strictly "normal" but it's common. You can see a doctor if you miss a second period. Best.

Period just starting: It sounds like your period is just starting. There is some normal variation in cycle length and this is within that normal range.