should I be anxious or worried?

So the glow app tells me I ovulate on the 27th. I started early testing with opk's on the 21st cause my cycle has been a little wonky the past couple of months. The opk's are only showing a vvvvvvfl. When should I expect them to start getting darker? I feel like today I should have a darker line than a couple of days ago but idk what I should expect cause I've never used them consistently. Well I'm using pre-seed this cycle so I'm really trying to nail down exactly when I ovulate so can someone help me understand what I should expect and how much should I test. Thanks in advance!