Opk question

Lauren • 31, partner is 35. We have two children, William 9 & Georgia 1. I am currently pregnant with baby 3. I work with domestic abuse victims in the north east. Partner is a roofer/joiner.
How negative should an opk be when you're not building up to ovulation. And by how negative I mean, does a pink test line always show or when you're not building up to ovulation is it meant to be just the control line?