Replying to Marijuana Fucked Me

This shit is serious so if your just gonna be stupid leave now... Thanks.

Alright so right now my parents are at Starbucks figuring out what to do with me because they found out that I've smoked weed and drank several times... They found out solely because my step dad is a snoop and looked at my gtalk (like AIM or MSN messenger) chats that were saved automatically by gmail and well i left it up not thinking. So my dad got back yesterday night from Europe, so my mom and stepdad have known about this for about 2 weeks... Well they obviously don't trust anything I say anymore. My dad is dissapointed in me and wants me to go to church and "life teen" now which is like having a terrible beating. Also their talking about me needing better grades to go skiing. And they don't trust me with my somewhat "girlfriend" and think all I want out of her is sex which is completely not true at all.

So they'll be back later and want to have a conversation with me. So what should I do or say to regain trust and have less punishment?