Ovulation

Ashley
This can be so confusing! I took an opk and got peak fertility on Thursday 10/8. We have BD'd every night since then. How do I know how many dpo I am? I guess it's difficult to know since you can ovulate anywhere from 24-36 hours after you get a peak LH surge. Just wasn't sure if I would count Friday as 1 DPO? Just trying to figure out when I can start testing.