PLEASE HELP!!

Danielle

Okay so I had sex on the 6th and my fertility was at its peak that day, and started spotting thick darkish brown blood on the 8th but I just had my period on the 29th so I don't think it could be that. Could it be implantation bleeding? Could I be pregnant? I'm on the pill and I'm afraid to continue taking it if I am but I don't want to stop taking it and get pregnant for sure if I'm not. Someone please help.