I didnt have my period last month and have taken three pregnancy test and they all three have been negative what should i do??

Reevaluate at 8 week: Are you using contraception or are you trying to become pregnant? Sometimes, a woman will miss one menses and start again at 50-60 d after last menses. If you're on birth control pills, you may have silent menses occasionally and skip periods. If you are not on birth control, be sure to take over-the-counter prenatal vitamins and avoid Zika virus. If you miss a menses at 60 days, see your MD.