Hi. I am 24 years old and I had a regular period of 4-5 days every 30 days, which start off heavy and stay heavy until the end of the cycle. For the past two months, after having unprotected sex, my period has show up two days late on boths times and have been light and last for two days. I ve also been extremely fatigue for the whole time, with frequent urination , and frequent headaches that I used to be able to take two tylenols for before but it does nothing for me now. I ve take two hpt that both came back negative. What could it possibly be?