Please help.. is the clear blue advanced fertility monitor accurate?

I'm wondering how accurate the ClearBlue Advanced fertility monitor is. Every month I get my positive opk "Peak" on cd 16. And just this month I have been trying to monitor my CM also, to see if they coincide. But I noticed a few days ago that I had sticky/EWCM and a lot of it. Almost felt like I started my period. (We baby danced that day just in case.) But which is more accurate, EWCM or the LH surge the monitor detects? Thanks! :)