They are waiting for you to confess. Dont worry, they wont attack you once they find out lol. Along time ago I had a blunt a friend gave me and it tasted and smelled like fruits with skunky fuckin weed. I smoked it out the bathroom window and I put it up in my room, turned the fan on and my whole room reeked. I couldnt believe the blunt was smelling that damn bad from a distance. All that day in school all I smelt was skunk from my pocket. While I was writing, walking all I smelt was weed and I was really paranoid lol. Anyways my mom came in and said "what are you burning?" and I said "nothing" and she said "mm-hmm" and never spoke about it again. When I finally confessed it was like she was waiting for me to say something and now she's cool with it. Your parents know and are not denying it, they are waiting for you to tell them.