Missed Period Help!!!!

Okay. So I’m 12 days delayed on my period but the pregnancy tests I took were all negative. The last time I had sex was February 22, 2 days after my period ended, and he didn’t ejaculate inside (he came on my stomach). We only did it one time.

Nothing much has changed with my routine, aside from me not eating rice everyday like I used to. And trying out Alive Multivitamins because my aunt said it was good. So I don’t know what’s wrong with me. I’m scared that I might be pregnant but the tests were negative. HELP!!!!!