Help please

I just need to hear some other opinions. Last month my period was 2 days early. I am very consistent on starting exactly 28 days later. Its usually only early if i have sex a couple days before i'm supposed to start. I should have started yesterday, my breasts are tender and my nipples are sensitive which isn't usually a pms symptom i tend to have to this extent. I took a clear blue pregnancy test yesterday but it wasn't the first pee of the day, it came back negative. Still haven't gotten my period yet.