A good alternate drug for weed?

Ok, well heres how it goes. I'm 13 years old and i started smoking weed every once in a while about two months ago, usually when my friends have it. (I don't buy it) But the in the last few months my parents, who also smoke weed + chewing tobacco and cigarettes, caught me after a "friend" snitched on me. So now they are drug testing me. I failed the first test about a month ago and I passed one last week. I really want to keep smoking but im afraid they will test me again and I will get caught. So what is a good alternate drug that doesn't show up on a 7 drug drug test? Also if i do keep smoking weed and do get caught with a failed test I'm trying to think of something to tell them along the lines of "Yeah, maybe I have smoked pot but I'm not going off doing anything that's really bad for me. If I smoke pot it will keep me away from those harder drugs but if you want to keep drug testing me I might have to switch to the harder drugs that wont show up on a test."