I done 2 tests both come back negative so i left it a few more weeks n took a clear blue and it come back positive i was only 7weeks gone and im now 17 weeks gone :)
Three weeks after a missed period would make you 7 weeks, not 5, Dani.
I have never had any issues getting a positive on an hpt on or before the first day of an expected period but some people who ovulate later in their cycle may not show a positive for several days after. First morning urine is best, and there's no need for expensive tests (the ones at the dollar store are just as sensitive).
My pregnancy test didnt come back positive until i was 5 weeks pregnant, almost 3 weeks after my missed period