CD33 4 days late. No AF and BFN

Idk what’s going on. It’s getting discouraging. I know there’s no way to know for sure if I ovulated because I don’t temp. But I had super light brown spotting for like 2 hours the same time I got my positive opk. So I would think I would have started by now. But I have absolutely no symptoms. PMS or pregnancy. Anyone have an experience with this? Did anybody get a negative around 18dpo then get a positive later? Or am I just out? Please help.