help!

Sasha

According to this app, I should've started my period yesterday, although I usually start on the same day every month ( last month I started on the 4th and ended on the 7th.) but either way, I'm late. I took a first response test this morning but it came up neg. should I just wait and retest in a couple days or am I just not pregnant? my fiancè and I did have sex on my ovulation day last month so I'm just a little confused.