Help!!!

So the other night my mom walked into my room and saw me and my BF of 2years smoking a joint, I'm 17 18 next month. My mom is very anti drugs so she went crazy, but then calmed down, I took all the blame and wasn't to fussed that she caught us, but my mom always holds onto things for years! and this is one of them, she blamed my boyfriend and I feel like she's going to try and stop things between us, it just breaks my heart because I feel like I've ruined everything how she now now hates him with a passion! I know it's wrong and it's a mistake but I'm my opinion alcohol is just as bad, it's safer at home than on the streets. I apologize to my parents but advise how to help the situation!