7-8DPO positive OPK?

🥰❤Mother of 1🧒🏽😍 TTC #2

So today I'm 7-8 DPO and I'm so over the 2ww 🤦🏽‍♀️😂 so I decided to pee on a OPK test for the hell of it to keep from using my HCG test and my test line is still showing 🤔.. I take my opk for 3 days after ovulation til nothing shows in the test line which it stopped 3DPO but today the line is actually very visible.. Strange right?? Does anyone know why it's dark a week past ovulation??