What Causes A Delayed Period And Negative Pregnancy Test?

hi this is shobha, i am 22 years of age. and i want to ask about periods.
the periods date for this month was on 27th of this july .but for today it has already been 14 days and my periods have not happen.
i had interaction once with my boy friend .
so this means i have consumed .?
weight -61..
height -5.2
and also i made pregnancy test using the velocit kit.
and in that it showed only purple color .
that means it has showed negative .
can you clarify on this ???