I felt like this too.
It's uni though, it's a totally different ball game. It's not as insanely hardcore like a small (lets face it) segment of students treat VCE, plenty of us here though. It's pretty relaxed and chill for the most part. First year for most generalist courses ("Science", "Arts", "Commerce", Etc.) is usually insanely broad. You may be taking a few subjects you dont want or shouldn't be in. I took chem in my first year and absolutely hated it. I failed one of the units. Things like this happen when its broad, you run the risk of getting something that isn't what you want or like. Even within the general first year subjects (Eg. BIO1011) you will find chunks you don't like. I loved the evolution lectures but hated the lectures on botany and plants.
So, when you specalise down a bit more (and get closer to what you actually like/want) your marks and/or interest just might improve. Now that i'm doing actual pharmacology and subjects for the most part i have a very strong desire to do/are my major, i feel a lot more engaged and willing to do work. It might be one of those things you just have to put up with and wait it out.
It's ok to not constantly have your head burried in books, in-fact, its probably beneficial. These are some of the best and freest years of your life, enjoy them.
I'd follow JinXi's advice. I really wouldn't jump ship based on anything *under* a semester, even then its a bit thin unless you hate the entire area (say science all together). That said, if you do realise you really dont like it or cant see yourself in it, after thinking about it and trying it out for a semester, i would encourage you to jump ship. There is no use in keeping pride or dealing with sunk costs, you really shouldn't go down with the ship. No one really cares about time in uni, people intermit (take breaks), go on exchange, take less subjects, fail, etc. So, losing a few years is no big deal but at the same time, you dont really want to throw away years or hard work either.