Can A Sinus Infection With Bronchitis Cause A Delay In Periods?

I am 2 weeks late for my period. I have been dieting for the last month, only eating 1200 calories, I've lost 4 pounds. I have taken 3 pregnancy tests over the past week, all with negative results. I do have a high stress job, and recently took the week off for a break. I am currently also dealing with a sinus infection and bronchitis. How much longer should I wait before calling the doctor?