earliest DPO you ever got a BFP!?

I wasn't tracking when I ovulated only watching my periods, got a BFP on cycle day 18 believe it or not it's true & on a dollar store test to beat it all, confirmed with blood tests as well... unsuccessful pregnancy though unfortunately so we are trying again! if I got a positive so early the first time is it likely to happen again? 
​when's the earliest you ever got a positive test? :)