Pregnant? Late period

I'm about 7 days late and I've been really worrying about it etc, I've just taken a test and it came up negative, I'm just questioning it because it's late afternoon? I've seen some topics suggesting it is less accurate (I'm hoping I'm not) do you think I can rely on this result and just relax and hope my period comes along? Or should I be worried? 
Thank you any advice would be really helpful I've not had to deal with stuff like this before. 
(I'm 20 but my boyfriend is quite new!) 
Xx