your 19 & your mum don't know you smoke.

right i would suggest: never admit it, thats what i always do & it's worked think of a story quik before anyone speaks to you, make it full proof & stick to it, never change your mind & say something different.
shouldn't be too hard if you've hidden all your drugs, just make sure no1 finds the drugs & there's no evidence. also if you can, get the peice of cardboard & burn it.