Is nausea an ovulation symptom? Also, which one is positive or peak?

I am at cd12 and decided to take my opk a couple days after af - which I don’t usually do - and boom - it’s positive. Maybe this is why I haven’t gotten pregnant (in addition to breastfeeding at now 16 months) for the last 6 months of trying. Anyway, the date and times to the left:

My husband and I did the bd on Friday, Saturday and Monday. What’s the likelihood we have conceived or will???? And would you say we had sex close enough to be sure?

This is our 6th month and the first time I’ve ever had a positive opk!!! 🤞