How many DPO am I and when should I test?

I had a miscarriage this month and have been super anxious as y’all can imagine. We had sex twice in my ovulation week but he finished in me ONLY on the 17th. I’ve been pregnant three times and with my last two pregnancies, I’ve tested positive at 8DPO and I counted that the day after we had sex. For example with this month, we had sex and he finished inside me on the 17th, I count 8 days from the 17th. I’ve made a post about this on a few Facebook groups and almost all of them said I am not at the DPO I think I am. So what do y’all think? I’ve tested on the 24th and on the 25th and it’s negative for pregnancy. Please be nice. Three pregnancies later and I am still learning about ovulation.