Clear blue fertility monitor help!!

I'm using the monitor for the first time this month as last month I never got a surge with usual opks. I'm am like clockwork... 29 day cycles every month! I believe I usually ovulate on cd17-18. I'm now at cd11 (or 12 if I count first bleed in the evening before) and still reading low on the monitor. Is this normal? All my apps say I'm in my fertile window.