true or not true?

How many of you think this is true? According to this stress affects only ovulation but stress around the time of an expected period will not cause it to be late. 
Anyways I posted this because I have very irregular periods. Sometimes it's at the beginning of a month and sometimes it will just change. But since I've been off of birth control for 6 months it always been at the beginning. Now I'm 6 days late and had sex a lot during my ovulation/fertile times. 2 negative test results so far.