HELP wondfo okp charting

Amanda • My husband and I have been married for 5yrs. We`re currently expecting #3 and couldn`t be happier!
For those of you who kept your OPKs to track your fertile long did you keep them? I'm noticing that, no matter how dark/light my test line was, when they dry, they all look identical. They're all obviously negative but I can no longer see which days were darker or lighter. I'll post a pic. Anyone have any suggestions or experience with this?