Period or implantation

Hey guys! So I had sex on October 3rd (used a condom but it slipped off) and was supposed to start on October 6th. Well my period never came. Then yesterday (the 12th) I thought I started but it was light pink and super light. Today it's been dark brown and super light. Normally my periods are medium to heavy and red until the end then dark brown. Any chance this is implantation bleeding? I guess I should just watch it for a couple days? If it is implantation bleeding how long do I need to wait to test?