I had unprotected sex on the week of the 6th of October. My scheduled period was supposed to come today 10/21/13, has not come. Could I possibly be pregnant?

Yes you could.

You had sex, so yes, you could be pregnant.

At this point, since your period was supposed to come today, you aren't even officially late yet. You need to wait until you are two weeks late to test. When you test, use first morning urine.

Yes you could.

Although, I was not planing on becoming pregnant, and took the "morning after pill". Could it have possibly failed?

Yes, it could have failed. There is no form of birth control that is 100% effective. It is also possible that the morning after pill has changed the course of your period.

There is no way we can tell you one way or the other. You now just have to wait it out for another two weeks prior to testing.