Lines disappearing?

Why is it that the closer I get to my ovulation date, the more faint the lines ard on my opk? This is so frustrating. Sunday was the first day I actually got two lines on my opk. They went the same color but I knew it meant that I'd be ovulating soon. Cut to this morning (two days before the big O) and the testing line is getting LIGHTER!!! I have been nothing but a ball of emotion because I'm starting to think a baby with my husband isn't a possibility. Almost 3 years of trying and nothing. Excuse me while I crawl into my dark cave of depression.