So I am now 4w6d, these tests were 1 and 3 days ago. I'm not a person who drinks enough water and I'm sure that has something to do with it. Hook effect is rare and even more rare in earlier pregnancy, but it can happen. This top photo was most recent, top test is regular and bottom is with diluted urine (55% water added)

These ones, top is regular, bottom is 55% water added. I just wanted to put this out there so if you're a serial tester and your tests start getting lighter, you can check with this method to see if hcg is simply too high for a home pregnancy test to properly handle, or if there's just not enough hcg.