Positive HPT, but it was faint?

I tested on June 5th (should have been the start of my period) I got a BFN, I also think this is the day I implanted, so maybe my cycle was supposed to be a longer one this month. Then I tested the 8th, FMU and it was a faint positive, and I tested again with my second morning urine, and faint yet again. Why are they so faint if some people can tell before their missed period? Is something wrong? I used one Equate then one First Response. Thank you!