Should I be concerned?

I use the equate and clearblue opk tests and the app predicts today is my highest chance to get pregnant, but none of my test lines ever got dark?

* I wait 4 hours before taking the test.

* I don’t consume any drinks during the 4 hour period.

* This is also my first month using opk tests.

This is my 5th month ttc. My husband and I are actually doing the “SPEM” (sperm meets egg plan) this month. Hopefully, we get our BFP, but I’m still concerned about not ever having a dark line.