Confusion with Ovulation

How difficult can it be to read an ovulation test? Yesterday I thought I got a positive. I was kind of shocked and excited since I just went off the pill. When I happened to look at the instructions again, it said the second line should be equal or darker to the first line. I'm not sure it was. I tried again today, and there wasn't a line. WTH? Was it a positive yesterday, and my window of opportunity has closed over 24 hours? (Not that it matters because I was only doing this to see if/when I ovulate.) Have I not ovulated yet? Who would have thought this would be so difficult? I guess I will try tomorrow to see what happens. I know, it's a cliff hanger. : )