OPK Tests... reliable???

I currently am using Clearblue opk. I am on cycle day 19 and they have all been negative. I started testing on cycle day 10 which is 4 days after my period ended.

Glow keeps pushing my ovulation day out.

Should I keep testing or is there a possibility the tests never picked up my peak day? Around cycle day 12-14 I had CM that was like egg whites. Now it’s more watery/clear.

Trying to decide if I’m outside fertile window or should I keep trying regularly just in case...?

Help!