There's meaning in everything unintended or not. From stereotypical 'great novels' to popular drivel. If you choose to see it, read into it and enjoy yourself why not.
Being pretentious is more the attitude of which you treat people who don't want to do this or don't care. Talking down to people because you the almighty student read meaning into the world and these lowly not students don't.
It's a trap easy to fall into at university because you are studying with people who share your interests. I've had conversations about all kinds of things and the meaning in them with university people. You get into a habit if you're spending your days with these people, living with them. Saying "I like batman" can become a philosophical debate. Then interacting with people not in that environment can sometimes be odd because you're so used to that mindset from your peers and tutors.
I almost exclusively hear the term "pretentious," and its cousin, "mental masturbation," used in the context of people who aren't into philosophy name-calling people who are; It's just a matter of people complaining about hobbies they don't partake in. Pretension is when you're trying to deceive people. You could spend the rest of your life trying to analyze the nature of reality out of the first line of a book, and if that's what you're interested in doing, then it's not pretentious.
All meaning comes from your own head, even at times when you think it's clear. Metaphor and applicability are in the eye of the reader. In no case can it be guaranteed that this will always reflect the author's intent, nor should it.
It usually comes from your head. There is little chance you get the meaning someone else had in mind if they meant anything by their writing in the first place. Maybe you're analyzing something written over a bottle of vodka. Then again who cares? If it means something to you good for you, doesn't matter what it was intended for.
That said, keep it to yourself -if you want my advice. If your friends are saying you've become a pretentious college kid it's probably cause you are discussing it with them and they have no inclination to hear any more about it. Then again you're 18 ...
Come to think of it, I have no idea either. Don't worry about it. And just because we don't know, that doesn't mean we shouldn't try. I doubt you're saying that, but on the off chance that's what you're trying to get at I gotta say something. Asking that every time we try to interpret anything will just leave us too afraid of being wrong to stand by any answer. I think the bigger, more intellectually destructive thing is for someone to try and find meanings they can USE (like someone finding a retarded niche analysis so they can scoff at people who didn't find it) as opposed to finding one we can understand (like someone finding an intended OR accidental but still purposeful interpretation, like the many that come from "Heart of Darkness")
I think it's important to remember that writers are telling a story. And a lot of us don't write while constantly thinking Character X's dog is a metaphor for the economy of country Y. Sure, sometimes that's the case. And sometimes stuff slips in that we weren't intending, but intent isn't really what's important. Ideology exists whether the author intends it or not. So I don't really think that work that you find meaning in -- whether intended or not (and usually it's probably not, or not as deep as you think it was intended to be) -- CAN be as pretentious as most readers/naysayers say it is. Pretense implies intent.