Just curious but are you certain when you ovulated? Temping is the most accurate way to know. OPKs only show an LH surge meaning you will PROBABLY ovulate with the next 48 hours (although an LH surge does not guarantee ovulation).
If I had gone off my OPKs then based on my dating ultrasound I would have gotten pregnant about 5 days after the positive OPK. OPKs can be off. I once had OPKs turn positive for a week straight.
i got positive opk on cd18ish (was over a year ago) but my 1st scan showed i must have ovulated at least 5-7 days after that date. Also with @June2016BabyW ive had week long positives. And they are easy to misread. I read the instructions 3 time but somehow still managed to miss that the there will ALWAYS be a test AND control line, but its only positive if the test line is darker then the control. And you can sometimes get multiple positives if you catch the surge on its way up and down. I used opks for 4 months as there were a handy tool (used correctly of course) but they are definitely only a guideline.
Re: Pregnant AFTER ovulation
The sperm needs to be waiting on the egg, not the other way around.