Ovulation help

I'm confused about whether or not I'm actually ovulating. I started using opk's in October. I used the digital ones in oct/nov and both were positive. I didn't get any positives in December....not even a faint line!!! This month I started with nothing, then got a faint line, which proceeded to gradually get darker. Then all of a sudden my test line started getting lighter again. I tested again that day and the next day and got the same result. So since I never actually got the dark line on the opk does that mean I didn't ovulate? There has been no change whatsoever in my bbt.