it could be but implantation bleeding doesnt usually happen until about a week before your period is due because after ovulation (14ish days after the start of ur period) it will take approximately a week for the egg to reach the uterus to implant, meaning it should be about a week before your period. ofcourse you coul have ovulated early or something. If you are on the pill and you missed one or more pills this could have caused it. It is funny you should post this because I had a similar problem this month. I am on birth control and two weeks after my period i had very light cramping for like 5 minutes and then I had a bt of brown dscharge that seemed to all happen at once.. it didnt last but it was quite a bit. The strange thing is this has never happened before and I didnt miss any pills. I am just waiting to see if my period comes on time tomorrow! fingers crossed