How old are you?

If it tests positive for THC well you could get some misdemeanor possession charges. Most misdeamnors can be punishable up to 11 months 29 days in jail and/or fines but the court and the state rather have the money or money with a little jail time or probation. Its about money.

You need to talk to your parents and throw yourself on your sword. You need to quit while you're under their roof it seems and while giving all that stuff to the police may help get you to quit, no good will come out of legal trouble and they need to be made aware of this and that you will quit. They may get an immediate result by giving you up to the police but they will sacrifice your future. You don't need a record because it may affect your future work ability. So what do your parents want? A child who has trouble getting a good paying job and because they have a dead end job this might cause more stress in your life and future and maybe even having a family of your own? Nothing good comes out of getting the cops involved as the way to get someone to quit marijuana.

You need to tell them you'll quit and do everything to quit. Don't make it sound like you're quitting because you live with them and when you move out blah blah blah. Convince them that legal troubles will only ruin your future.