Same with me, one of my preg didnt test positive until 8 wks, and as the others have said use first morning urine and the dye tests
I didn't get a positive on a hpt till I was 8 wks pregnant so it just depends if ur hormones r high enough
Have you made sure to test in the morning and what type of test are you using? I always use an EPT test, generic tests have given me false negatives before.