Don't think I ovulate

Hi everyone

We have been TTC for 4 months now. My cycle has started being irregular for about 6 months now drifting between 25 and 39 days. I'm currently CD18 and still have negative opks. I've been testing twice a day so doubt I have missed it.

Has anyone else had negative opks this late in their cycle and still got pregnant? There isn't even a faint 2nd line most days. We have BD every other day since CD 6, just incase this was a 25 day cycle. I really don't know what to do next?