Implementation bleeding???

So I took an at home pregnancy test Saturday it came back negative, on Sunday I notice some brownish when wiping I thought my period was suppose to start today Thursday November 9th but it started Sunday November 5th, but I now think it could be IB four days before.... I’ve taken two more test both still negative.... but the bleeding hasn’t been heavy or changed in flow.... thoughts? Am I pregnant and I’m just not testing positive? How long until I would test positive after IB???