OPKs and their accuracy

Shana
Has anyone else used First Response Fertility and feel that they may not be all that accurate? Based on Glow, I'm meant to have had my peak day yesterday, no I haven't got the two lines to be exactly the same color yet and I'm on Cycle Day 13. 
I'm a little concerned that maybe the tests aren't strong enough or there's something wrong, or maybe I'm not getting an LH surge. Anyone else have experience with this/advice? Thanks in advance!