Brown Spotting instead of period

I am 26 years old and have a very regular cycle. I am sexually active but have not had sex in about a month or five weeks. The problem is that about a week and a half ago, I started having brown spotting everyday. It is the same color and consistency as the end of my period usually is, except a) I haven't had a beginning of a period and b) it's lasted almost twice as long as any period I've had. Occasionally over the last ten days, I've had some red spotting but nothing has been heavy enough to warrant the use of a tampon. I have not had any cramping that I can recall but have been overstressed in the last two weeks.
This has never happened to me before, although I recall being as stressed out before. I am concerned that, given the timing of my last sexual encounter, I may be pregnant, but am wary this could be stress related as well. Can someone shed some light upon this?