Possibly Pregnant?

My boyfriend and last had sex on the 7th, it's now the 16th. We use the pull out method as we both dislike condoms. I am not taking any birth control and my period is due on September 26th. 
​Three days ago I started to have what appears to be spotting. It was a reddish brown color the first day, and gradually has become just pink after three days. I have never had spotting this early before a period, or ever had spotting at all.
​Is it possible that I'm pregnant, or that my body would even be showing signs this early? How soon would a pregnancy test be accurate in this case?
​I don't think it's very likely that I am pregnant, but there's always a chance any time you have sex, and I'm just not set up to have a kid yet. 
​Thoughts?? Thank you! :)