Brown stuff

I guess you can say my period ended 3 days ago? I just wiped and there’s brown stuff. I know it could be old blood, but I don’t remember if this always happens this late. I did have unprotected sex on the 26th and he did cum in me. Could this be implantation? Could I be pregnant? I have no discharge yet so I don’t think my fertile window has opened . It says it opens on the 31st on this app and I ovulate on the 5th and on another app it says the 30th and the 4th