My last period was on the 31st august, i had unprotected sex on the 10th september, 4 days after i noticed light pinkish blood colour when i wiped, then i started having alot of brown discharge, i put a tampon in that night and the next morning the tampon was covered in blood? but im not due on my period for another 2 weeks, what could this be? ive heard alot about implantation bleeding, but is it possible for it to be that heavy? really confused can anyone help?