I agree with Adgal. I had implantation bleeding with this pregnancy, and it only lasted 1-2 days if that. Spotting is light brown/pinkish red in color, only a few drops...should not be any heavier than that, nor should it last 5 days. Good luck!
Implantation bleeding is actually quite uncommon, but most of the time it is just a tiny amount. Have you taken a pregnancy test yet? It could also be a very light period, or mid cycle spotting, which can be caused by low progesterone. Good luck to you.