Missed period !

They usually last 4 days I’m on day 5 , first day of last period 10/7 I tested with cheapies Friday Sunday and today all negative maybe I need to try name brand ones? the only thing I feel is like I have a stomach virus I threw up the night before like what I ate didn’t sit well and I have light cramping/pain. 1 yr TTC I’ve never been this late AF is usually on point with app prediction so idk what’s going on !!!