Conflicting Readings...

I have been tracking ovulation now for 5 months and use the Clearblue Easy Fertility Monitor as well as the Clearblue Easy Digital Tests for back up. The reason I do this is because after reading several reviews I found that the fertility monitor can falter. Anyhow I now have 2 different readings. I am trying to log my results into Glow but which one do I use. My monitor is reading "Ovulation" while my digital test isn't picking anything up. Has anyone else had this problem? Also I am only 11 days into my cycle which is a regular 28 day cycle. I usually ovulate at day 14, is it really possible that ovulation would vary each month? Any information and advice is welcome. Thank you!