help! when should I take a preg test!?

I'm 7 days late and I'm so stressed. I don't know if I'm late because I'm so overly stressed with school and work, or if I'm actually pregnant. What I'm trying to say is if I take a pregnancy test now, will I get a somewhat of an accurate reading or should I wait another week for my period. 
I'm just so terrified of being pregnant, so I'm kind of scared of taking a pregnancy test.