I had sex on nov.27th about 2 weeks later i had my period on time. i am supposed to get my next period in a week but for the last 4 days i have had brown spotting. enough to fill a pantyliner. i am on birth control and i have taken 2 home pregnancy tests and they both came up negative but could this be a sign of pregnancy? i'm scared. im not ready to have a baby, please help!