Opk question

Lauren • 31, partner is 35. We have three children, William 10, Georgia 2 & Eliza just born. I work with domestic abuse victims in the north east of England. 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?