Confused about ovulation tests

Abbie • 28 👨‍👩‍👦‍👦

I'm supposed to ovulate tomorrow according to this app CD 17 I've been taking ovulation tests since CD 12 and they are all so light. I thought they got darker the closer you got to ovulation? I've been taking them with fmu and before I sleep and by light I mean I can barely see a test line. I know they're supposed to detect a surge but can it go from barely anything to a dark line?