I had a yeast infection about a week and a half ago. it's been treated and is gone but now my period is 8 days late. i took a test and it was negative?

Late period: Reasons for missed / late period include: an anovulatory cycle in which no egg is released, marked v or ^ in weight; eating disorder; Over-exercising (endurance athletics), stress, travel, significant illnesses, oral contraceptives & other meds, Illegal drug use, breast feeding, hormone imbalances and medical problems (i.e., PCOS). Pregnancy is #1 reason.

Possible pregnancy: You could still be pregnant. You should follow up with your primary care provider to receive further testing to be able to make a definitive answer.