I'm not replying you on whether you should switch course
to read Mathematics instead of Physics, I'm only
making some comments :
" but when I do the questions, I realised that I still
can't get it. I don't know why is that so. Is it because I'm inept?
Or my study methods are wrong? I do all my tutorials, past year
questions but I still can't do most of the questions in
my exams. "
No it's not because you're inept or incompetent or
uninteresting as a person. It's because you're inept or
incompetent or uninterested in physics. It's two completely
unrelated issues.
Put it another way : if you're theistic, think of it as we're
all created as unique individuals with unique skills, interests and
strengths. If you're atheistic, think of it as our unique DNA
determines us as unique individuals with unique skills, interests
and strengths.
Two equally (and highly) intelligent persons. One could be a
physicist/pianist/meat-lover/religious/IT-expert, and the other
could be a
biologist/guitarist/vegetarian/atheist/martial-arts-expert. And
each might well be a complete idiot/inept/incompetent/uninterested
in the other person's field or expertise.
Doesn't make one right and the other wrong. Or one better than
the other. Just makes them unique from each other.
If you honestly find yourself struggling with Physics and don't
enjoy it anymore, go ahead and read something else (that you find
more interesting, whether Mathematics or something else) in
the University and base your future career on something else. Life
is too short to be miserable or wasted.
(Regarding the theistic vs athesitic scenario, I made mention of
it coz I was just reading a guestbook conversation on a Dr House
blogsite, between an atheist and a religious. For those interested,
I've reproduced the conversation in the Crapbox thread
stickied.)