I feel left out with my friends for weird reasons!?

OK so the other day i found out my two really good friends took some "Mary Jane," I wasn't surprised that one of them did, but the fact that the other one did really shocked me. He is the most, i guess, good kid. Last person you would expect. It has changed my whole view on him. And this is gonna sound really weird, but i kind of feel offended that i was not asked to join them. I would have said no, but i feel left out. I am so confused!! Do they think i am too good for that stuff, because im not that kind of kid and they know that! I dunno, i just really had to get this off my just because the feeling in my guy and head is unbearable.