Confused...pregnant or chemical pregnancy?

Hi ladies, so last week I did several home pregnancy tests including the dip as well as the digital ones. They all said positive. Went to the doctors on Thursday and did a blood test, result came back the following day as positive. Saturday I started to spot brown not much had some on panties and you can see it when you wipe. Same thing for Sunday. So I did digital clear blue test and it said 'not pregnant'. Did another test but this time the pee on a stick type and it was positive. Anyhow today is Monday and it looks like my period is here...a mixture of brown and red blood. Did another pregnancy test and it's still showing positive. Is it normal to still get your periods? Or it could be old blood or a chemical pregnancy?