Help I know how to ctb but my family is getting in the way

[somi.c]

So I've decided to inhale helium gas and die by asphyxiation. But the problem is after last time when I bought SN and my sister found it and showed my parents they keep my purchases under control also I'm 18 and a high school senior and my parents want to control me so much that they don't let me get a job, go outside without their permission or have a bank account. SN was my only hope out of this hell but my family threw it down the drain and now I really need to die but I have no idea how to do it while my parents are watching my every move. Also they don't love me they just don't want to tarnish their reputation

 

[ipmanwc0]

the only thing i can think of that wouldn't be waiting until you can move out is a train or jumping (hanging is an option if you can steal a rope)