Implantation bleeding?

Echo
So I had my period from August 3 to August 8, and had unprotected sex (on purpose) 4 of 5 days of my fertile window. Which was August 11-15, and I'm having very light bleeding. My period isn't due until August 26th, is it possible that this in implantation bleeding? My head hurts, I'm kind of nauseous, and my breasts are sore. Is it too much to hope for?