I am almost 19 and have been seeing my boyfriend for over 3 years now, On September 4 which was a Friday he came to visit me and stayed until Monday. We had unprotected sex on Saturday and on Sunday(Which was the day I start taking my inactive pills) I started my period on that Tuesday as I normally do, and then started taking active pills on the following Sunday, I have never missed taking my birth control. However on October 6th I did not start my period, and I didn't have my period at all. But a few weeks before I had Swine Flu, my parents were arrested, and a number of other stressful situations have occurred. Here are my questions.

1.) Could being sick and all of the stress have caused my missed period?
2.) What is the likelihood of me being pregnant?

Thank you for your help.

1.) Could being sick and all of the stress have caused my missed period?
2.) What is the likelihood of me being pregnant?

50/50

Birth control pills are 99% effective but sure, you could be in that 1% that got pregnant.
You will find out when you take a pregnancy test in a few weeks time.

Stress can easily mess up your cycle as well, again, you will find out in a few weeks when you take a pregnancy test.