Different OPK, different reading?

We are 2 mos in to TTC. Using opk's for about 6 mos now, and I am trying the brand Wondfo from Amazon. Not sure if I trust it yet so I am using my Answer brand too. Think I'm at My LH surge per the Answer- but Wondfo says I'm not quite there yet? Any suggestions? Also- cervix is starting to rise, not quite EWCM. bbt hard to say since I was on steroids for bronchitis lady week but it's slightly elevated. Your thoughts? ​