Pregnancy blood test ???

Lex • Seven years not preventing ( TTC ) one year doing everything possible. Young in love , want to start a family of our own
So I'm seven days late as of today , which is so werid for me , I'm never late !!! I've taken five hpt and all came up bfn so I got a blood test and it also came up negative .. I'd only be three weeks if I conceived ,, is it just hopefully thinking that the test was wrong , has anyone had a blood test come back negative and they were actaully pregnant ????