Need help with opk

Lucya

Ok so this is the first time im tracking my ovulation but have been ttc for almost three years. So im on my 18 day in the cycle and fertile week is april29-may5.

Now i feel like all my test look slightly the same, but today does look slighty darker which is a good thing right? Now do i only test during fertile window or keep testing until i get a negative for opk?

Also i have pcos and taking provera and metformin dont know if that matters at all