H.M.
I'm 7 weeks right now.
I got a faint positive starting on 10DPO with the dollar tree tests. They have a sensitivity of 25 BUT they never show anything more than a faint line.
I took test every single day after that (various brands) and it always came up positive. So I've seen those early pregnancy tests work. I didn't get a single negative after 10 DPO.
Oh and there is this great website that shows the sensitivity of most tests. It's peeonastick.com
check it out. It will show you what tests have to have an hcg level of what to show positive plus it shows some results on false positives and evap lines. Very informative!