Brown spotting for 10 days... Please help!

I have been having brown spotting every day since June 4th. It has been light to medium spotting, but always brown - never red or pink.

My regular period is supposed to begin today or in the next couple of days. I have not taken a pregnancy test since I'm on birth control pills, and the chances of being pregnant seem slim.

My doctor changed my pill a few months ago when I had similar spotting for about a week. I was on Caziant, and now I'm on Junel (microgestin), which I have been taking for almost three full months. I'm currently on the last week of my third full pack.

Does anyone know what could be causing the spotting?! Could my body still be adjusting to the new pill or should it be adjusted by now? Could it be extended ovulation spotting?

Thanks in advance for any input. This is my first post on Glow :)