Replying to My parentals found out that i smoke trees and drink...

Okay so I use Gtalk (Google Talk), its like AIM or MSN Messenger... Anyways I've been living at my mom's house since September 1st since my dad and bro are in Europe right now. So Sunday night I was on Gtalk and left it up not really thinking anything about it. Well the next day my step dad (Joe) got on it and looked into my chat history because it saves every chat that I've ever had... Well the chat history contained stuff about setting up parties, girls, drinking, and smoking weed. So he went ahead and printed all this shit out. Showed it to my mom and Monday night my mom comes to me and says "We need to have a talk", I thought it was about some essay I wrote that my teacher thought was disrespectful. But it wasn't... So we had a long conversation about how marijuana is illegal and that it if i got caught I could go to jail and all... And that pot leads to other drugs, which i told them I haven't tried and I would never even think about trying, which is the complete truth. Joe even said to me "Pot is worse for your lungs than cigarettes...", so I just stopped and looked at him and said "No, actually cigarettes are worse for your lungs because they leave your lungs coated in tar.". And then my mom cried a little bit. Then they talked about girls and how I shouldn't talk about them in the manner I do. haha They went on to talk about underage drinking and how I could get license suspended or some shit if I got caught. So They want me to not do any of those things again... But I really haven't experienced that sick highschool party yet. What should I do?