Spotting to light flow x5 days instead of normal cycle. What could be cause? Neg preg. Test.

Could be normal. This very well could be normal. It is not unusual for women to have a little bit of variability in their menstrual flow, especially if you have been under any recent physical or emotional stress.
Probably normal. Some women will have lighter or heavier periods depending on a variety of factors. Your stress level can certainly affect it, including but limited to missing a period or having a lighter or unusual period.