I NEED SOME HELP/ADVICE LADIES ONLY!!!

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Hey Ladies,
My monthly visitor is a little of two weeks late! I've taken about five pregnancy test and they're all coming back negative, but yesterday I got on test that had two lines (positive) but the one line was very faint, and a few hours later I got another negative test it was a clear blue test that read "NOT PREGNANT." Now, my manager who is currently on the weight watchers diet but hasn't been sexually active for quite sometime is ALSO late but was a result to her dieting. On top of all other things I am also sick with flu/cold like symptoms- tired, achy and mostly a bad cough.. to the point of vomiting sometimes. I have an appointment with my OBGYN to possibly do some blood work! Back to my question... has your period ever been late due to dieting or exercising? Please lend me some help and support it would be greatly appreciated <3