O date help!

So, I’ve been charting for months and I feel that FF is usually very accurate. However, the last two months it’s been giving me an O date and then after about 7 days, sliding my O date back. What do you ladies think? FF originally said I O’d on CD 13, but this morning moved it to CD15.

I know it’s not a huge deal, but I was planning on testing (early, I know) tomorrow because I thought it would be 9 dpo! Before you say don’t, this is cycle 9 of ttc and I’ve done all the waiting until appropriate dates, waiting until my cycle starts, waiting for 18 high temps, etc. and the pain never gets any easier when you see a negative. I wanted to change it up this month. 🙃

Help!🤣