Okay I'm going to get straight to the point!
I had unprotected sex (mistake) about a week or two ago. And I'm on the PATCH which I've read and been told is 99.9% affective. And I'm suppose to get my period this week its been two days and still nothing, but today I've had a light light brown discharge nothing big the amount of lets say the size of a regular lighter. Not much. And I Don't want to be pregnant. What do you guys think?

It's possible that you could be. No form of birth control is 100% effective. There are people on this site that used three different kinds of birth control at the same time and still became pregnant. It happens.

You'll have to wait and see. If you skip this period than try a home pregnancy test.

The light brown discharge is likely your period getting ready to start. Certainly, as Alty said, pregnancy can be possible even with birth control, but if you have been using the patch correctly, the odds are quite low.

Oh hey, this is a coincidence I've heard of a clear beige fluid emitting from a vagina before. From my experience, this means you're definitely pregnant. Take a birth pill?