9 morning behind time interval!?

My period is exceedingly unpredictable but it usually happens the final week of the month or the first week of the month..and I'm about 9 days slow now! I've taken 2 pregnancy test..all refusal.
I changed my diet in the second month and have lost 10 lbs (cut out soda and unwanted items food)..
I'm also stressed due to college semester starting last week...
Could that be it??
warning? I'm so worried! i would say btw the diet transform and the stress you are late. sometimes us girls' menstrual cycle change.
i do think it is your form that is the bring of your late time. n probably not pregnant. if you can go to a clinic and win a regular checkup explaining your late interval. excessive exercise(or much stress on the body) can change its majority function.