Can someone explain?

So as you can I’m in my fertile window and I’ve also been taking mucinex but I haven’t had ANY CM or anything like that. I’ve always been on time with my window and ovulation, I been trying OPKs and it says I’m not ovulating. But I usually am around this time??

My period was also very very light, light enough to just use a liner and it was only once a day. I also had a cramp like pain for about 5-6 hours last night.

Anyone have any idea?