When did you get your earliest BFP?

So I went for an ultrasound thinking I was 6 weeks based off my LMP. But we were only able to see 2 tiny sacs. They said Im probably not that far along and to come back in a week but if I am any less than 6 weeks then that means I got my BFP at 7DPO. Is this even possible? With my 2 other children I didn’t get a positive until almost 14DPO!