yes brown blood is old blood.. it could be from your implantation.. if there is not a LOT of it, and if you don't have cramps and it doesn't turn into red discharge i think your okay :) are you using a daily pad or a period pad? use a daily pad, and if it doesn't soak though it, then thats not much and it should be okay..but call your doctor if your worried about it :) no need to stress when you can just find out :)
I had brown discharge when I was 6 week. They told me that it was old blood
You should call your doctor. Brown discharge usually indicates presence/occurance of blood