2o days after the last day of your period? It may just be your body's way of getting ready for the next period, but if you are worried or unsure you should probably see you GP
Brown blood usually indicates old blood. This spotting could occur for several reasons including implantation or even stress. If there's a lot or it's very heavy, I'd recommend contacting your ob/gyn.
Sometimes woman have implantation spotting. This will cause a lil bit of brown or pink discharge. It sounds like you may be pregnant.I'd wait a few days and take a pregnancy test.. good luck!! Hope the info helps!!