BFN! :/

I'm currently 6 days late for AF and I've had a negative urine test and negative blood test at the doctor. what the heck is going on with my body :/ I'm always like clockwork every month and am never late and I have all kinds of weird feeling.. I'm peeing every 20-30 mins, nausea, vomiting, back ache , extra emotional , mild cramping ( not like AF) and I'm soooooo over tired! Any ideas?