light pink/brown discharge and period due in a day?

My period isn't due until tomorrow March 29, 2012...I went to the restroom this morning and wiped and my discharge had a little pink in it...now its kinda brownish like it is at the end of my period. I don't spot before my periods so this isn't normal for me. At the beginning of March I thought I was pg because I was throwing up for 2 weeks and a little sensitive to some smells but then it stopped. I still throw up every once in a while but I took 3 pregnancy test and they were all negative. I ALWAYS know when Im about to have my period because I cramp right before it but I'm not cramping at all. I'm just not sure what to think.