I'm NOT pregnant and 11 days late?

There may be an underlying issue why you are so late. It might be nothing to worry about but you should call your gyno just to get checked out. I have whacky periods and that's because I have a blocked fallopian tube. I also know some people who have PCOS. Or it could just be from stress. Are you active with sports? that could also cause it. And if it has been longer then 35 days, your doctor may prescribe you provera to make you get your period. Good luck but don't worry until you call your doctor.