This is my first month using OPKs and I need some help analyzing this one. I got some of the Wondfo (cheapie) OPKs and I've been using them all week and for the first time today, I got a pretty dark second line (it has been really faint before).

Is this dark enough to be considered positive? If not, should I try again with another test sometime before tomorrow afternoon (say tonight or with FMU)?