Keep testing. Do not do or take anything that could harm a potential pregnancy until that test is negative.
I had a full on 5 day "period" when I was pregnant with my 4th. You absolutely can have heavy bleeding during pregnancy that seems like AF but it isn't. This can be a lost twin, placenta previa, SCH, bleeding from the cervix, or a bit of lining sloughing off. Baby can stay stuck despite all this.

