In my last 6 to 8 cycles I have the same type of brown discharge befor a full flow. I am TTC and still I was not pregnant. When I described this spotting to the OBG she explained that the brownish color is due to an acid enviroment that the blood stays in before is time to get out and because of this we are not seeing a bright red from the begining. Now if her explanation has a foundation or not, I wouln't know. I am just saying how she explained to me. I also though several times that maybe I'm pregnant. Sometimes, especialy when you're ttc or thinking in a way or another about pregnancy, you start seeing signs even where there're not. Of course there is a slight chance of being pregnant and instead of wondering you can just do the test, but based on my experience, these brownish discharges might not be a sign of pregnancy.