Help i think i'm pregnant?

okay i've been worried the passed week, my best friend got two pregnancy tests (just a cheap on from the spar blue dye) and she made me do one with her and it came up as me being pregnant?! i don't know if it was a faulty one or what but my belly is usually flat and i've got bump there now my mum said it's a ''beer belly'' i'm freaking out?! am i pregnant? i'm only 16 my mum would kill me and the nurse at my doctors hates me she's such a ***** i don't know what to do :(