Why is my last period? I'm not pregnant or stressed!?

My periods have been regular for years, but is almost a week late. I took several pregnancy tests all negative. I looked up information on drugs and net say in menstrual periods may be caused by pregnancy, stress y. I'm not pregnant, stressed, or drugs. Could it be something serious? Furthermore, my diet has not changed. I eat normally and I am not overweight or underweight. Not much exercise either.

If there was something serious I would have found if you looked for information on the network. It may be too soon for a pregnancy test?

You Will Never Love Me ep 16