i need answers!!

tomorrow makes a week that AF is late.. (AF was due jan 19th) i have light cramping here and there, i'm tired a lot, but absolutely no signs of bleeding. i've taken 3 tests, 2 different brands... all have been negative. what the heck?! i'm not on birth control, so i know it's not from that.. i'm just so confused because i feel like a dr will just try to tell me it's normal. but it's not! i've been off birth control since september, and this is my first period that isn't on time! any advice??