Is it normal to feel outcast?

The situation that I'm in is hard to describe, and sort of a long story but I'll do my best to explain it. I've always been a friendly person, and I like to think I'm easy to get along with - I don't usually have problems with the right friends or popularity complexes or trying to comply with what the average person thinks of me. I've always had my own circle of friends, and I thought we were a really tight bunch, but now everythings changed. I'm not gonna go into full detail here, but early last year a lot of my friends "discovered" drugs - namely pot/marijuana/weed/cannabis, whatever you choose to call it. It was a laugh for a while, and I was sort of attracted to trying it out by a sort of morbid fascination, curiosity, and that oh-so-cliched idea that "everyone's doing it!". It wasn't the first time we had gone through something like this - about a year previously, we had "discovered" booze in pretty much the same manner. I was never into either substance as to say I was a stoner or a drunk, but yeah I indulged in them with my friends. We had a laugh and that was that. However, it didn't carry on so well.. My parents took me to a random drug test, and I was pretty much busted. I was isolated from my friends, and shortly afterwards, the same thing happened to one or two of them. The weird thing is, I think that they assume that I ratted on them, because ever since that happened, they pretty much isolated me. They all ignored me, didn't want anything to do with me - one of my very best mates for well over 3 years hasn't spoken to me since the beginning of this year. He makes an obvious and outright effort to stay the fuck away from me no matter what. I've tried confronting them about it, but they just ignore me or walk away (same thing I guess). I only have one or two friends now.. And the only person I confide in is a girl that I haven't even seen for months. I don't really want to talk about it to anyone else, because they wouldn't understand where I'm coming from. I know it sounds like a really small matter, but it's eating me up inside. I feel completely outcast...