Hi! I'm 28 years old and single. My last period started on July 11, 2013 and ended on July 16, 2013. My cycle would sometimes be 26, 28, 33 and the longest that I had was 37 days. I had my last contact with my boyfriend last August 12, 2013. I have been waiting for my period up to now. Today is my 40th day cycle. I had a pregnancy test last 14th, another on the 15th and on the 16th and it all revealed negative. I have not taken another test until then. I'm worried. Could it be possible that I am pregnant? Please advise. Thank you.

It is very possible but without a regular period knowing when to test is harder, at this point, you need to be at LEAST 14 days late just to start testing. Using your longest time, then you are only a few days late now. So best opinion, wait another week, and test, then if negative, wait another week and test again.

Always use first urine of the morning as soon as you wake up

Thank u Fr_chuck for the response. I also forgot to tell you that I was also diagnosed to have PCOS last 2011. I had taken pills for 3 months as prescribed. I haven't undergone another ultrasound since then. Does PCOs also affect the delay of my period? And another thing more is that I just had a 9-hours flight last 16 . Is it not considered as a stress on my part? Please advice. Thank you and God bless :)