thank you for your query.
After 3 negative tests, it is rare that you would be pregnant.
However, confirmatory would only be check up with a gynecologist and a blood B HCG test or a pelvic ultrasound
rarely, a light period could be a normal occurence.
Other causes that could be involved are stress, anxiety, weight gain or loss, intake of hormonal
medications in the previous cycle, thyroid
disorders or polycystic ovaries
if you fail to have your normal period in a day or two, you would be best advised to consult a Gynecologist.