My period...

My period is usually on time or just a day late. I've had to say that my period is late twice now when I log. I have taken four tests and they are all negative. Supposedly my period is to show today, it's 1:27am here, and I just don't know what to think... I guess if Auntie Flow doesn't show by the end of next week I'll go in to my doctor. Any thoughts? Thanks!