OPK test

So I just started using opk tests about a week ago. The first couple I took did not have a second line , but the 5 or so after that have a second line which I thought was getting darker a few days ago but the passed couple of days the lines have been the same ( not dark enough to be a positive)

I didn’t start testing till about one week after I stopped my period. Is it possible I ovulated before I starting testing? Any thoughts? My fertile window just keeps expanding on the app because I’m putting negative opk in but I really don’t know :(