Possible chem? Or bad test?

So I started AF 6 days early this month. She was medium to heavy Monday- yesterday and today she’s barely there to where I didn’t have to change a light liner. I decided to test just because I had 1 left and we are going to wait to try for awhile after this month and a faint line showed. Think it was a bad test? Maybe had a chemical? Or possibly actually pregnant (I know slim to none)?