AF come but still BFP?

Has anyone ever had a period and gotten a BFP? I started a day late but only bled for one day then spotted for two days. I've had bad nasuea and fatigue but I keep getting a BFN plus I thought AF came it was just odd. I don't think it was implantation bleeding but maybe. I just assumed that wouldn't happen during my normal AF time and that I would get a BFN.