Why do I only get 1 day of +OPK?

Hi. I have PCOS. I use clearblue easy digital OPK's and monitor CM. I see a lot of women on here who get 2 days of + OPK results. I always only get 1 day of + OPK's. I also get alot of EWCM on these days and a couple days prior to +OPK. I usually test at least twice a day, sometimes more. Is this ok? Why do some women only get 1 day and others get 2? Can I be sure that I'm ovulating.

THANKS!