my period is 6 days late!!!

Sara
My period is 6 days late and I'm really wondering what is up! It's never late I'm always really ok time and I'm freaking out! I can't be pregnant because I'm a virgin but that just means I could have some sort of health problem which is worse in a way! How long should I wait to talk to a doctor? 
UPDATE: it still hasn't come when should I start being worried???