Explanation/thoughts?

Hey ladies. I'm 8mo pp. My period returned when I was 6w pp. and has been normal (I have pcos and amenorreah and this is the most normal I've been since puberty). Last week I was feeling ill: dizzy, nauseous, etc and I took a PT on Tues and it was neg. I've been waiting for my period as it has been regular the last 6.5mo and I realized today (appx one week since I took the test) that I am 7day late! My period waa supposed to start last weds and it hasn't begun. Is it possible I took the test too early or that my body is going back abnormal?