Pregnancy test accuracy

Justice

Hi ladies,

It has been about 27 days since I had unprotected sex and took a plan b. I am now 4 days late on period and been having pretty bad cramps in my uterus as well as nausea and headaches for over a week now im still with negative pregnancy tests, possibly from the plan b idk. Would a pregnancy test be accurate by now? I know some of yall get more accurate tests different than what the package says. Just wanted some advice elsewhere thank you!