Take another test?

So i'm currently 15 days late. my period is definitely not the most regular, but it's never been this late. I took a pregnancy test yesterday and it was negative but i'm still a bit worried. Should i take another test or wait it out a week? What are the chances that it was a false negative?

i'm also not currently on birth control- and i dont need comments to "be more careful" 🙂 thanks