I m not sure how to approach this but me and my girlfriend have been sexually active recently but ALWAYS use a condom which i examine before hand and test after for holes. Her period is due the 21st and on that date it seemed to come, usual for her, a few drops (not spotting according to her) of normal color blood. the following day, nothing and again nothing the day after that. i am worried but she does not seem worried yet, we are both 18. please help...could this be implantation bleeding