How much blood is considered implantation bleeding/spotting?

I had unprotected sex last week and for the last couple of days I have been feeling nauseous and I don't feel like eating as much. My breasts arent sore though. I started bleeding about 2 days ago and it started off dark brown brown blood and now it's red. It doesn't feel up my pad because I change it every 4 hours or so but there's a medium amount of blood on it and lots of blood when I wipe. Is this my period or is it implantation bleeding?