Opk??

Des • US traveler. OR living. RH Neg life yo.
I've started doing the ovulation tracking and I picked up an opk. I know there are suppose to be two lines all the time, and when your ovulating you judge by what lines are darker. But I haven't gotten two lines at all, ​ The results have been really inconclusive so far. Do you think it's just a bad batch of them? Has this happened to anyone??