I use those tests and in the beginning I never got anything anymore positive than that. BUT... that was when I only tested once a day.
In later cycles I realized that my LH surge is short and I most likely was really missing my TRUE positive.
I have 28 day cycles usually Oing on CD14.
So I would start them on CD 10 and test 3 times a day. Then when the line started getting darker I would test everytime I peed. Once I started doing that I always caught my surge.
Your tests aren't quite there yet but I'd say you will get a positive one soon.