I'm tired of being the fuck-up

My parents have always made me feel like the fuck-up.  Next to my perfect sister, whom they dote on, I'm just average.  I'm not smart enough, not polite enough, not caring enough -- simply not perfect enough.  I've always been inferior, and now that I'm off to college I'm even less perfect.  I won't get full ride anywhere, and even though I refuse to let my parents pay for anything, they still know I'm nowhere near as wonderful as my sister.
So I started cutting six years ago to deal with the issue, and after repeated "talks" with my parents about that, I moved on to smoking pot every now and then. Fine. Whatever. I like being happy every once in a while; I like not feeling guilty for eating. Okay. It doesn't seem so bad. So it's illegal. Whatever. So my mother just found out about that (through snooping, which she needs to fucking stop doing) and now makes me feel like more of a fuck-up. Maybe I am, I don't know. I just know that I'm frustrated and can't trust my mother.