Need help I understanding ovulation/conception

So I had a miscarriage in 2012 that ended in an emergency d&c after that  my period was off before my period would be like 5-7 days and very heavy. After the miscarriage I would bleed for two days then stop completely for a day then bleed one last day. Well I was having unprotected sex for like 3 years and getting BFN well I decided to do BD on that one off day that I started bleeding and bam I'm pregnant. Now that month I bled on the 5th the 6th stopped bleeding on the 7th (had BD that day) then Bled again lightly on the 8th my discharge became very creamy afterwards and I've never really had creamy discharge before. Well I also did BD on the 21st and 28th of that month and according to my LMP my estimated date of conception was around the 18th. I got my BFP on the 8th of the next month which would've only been 2 weeks from the 21st. My question is it possible I got pregnant on the 7th or is it more likely I got pregnant on the 21st. During those three years of TTC I never had BD on that one off day before. Sorry it's so long I'm just trying to understand it all.