Information on tuning a piano?

Okay, I'm fourteen, and I've been playing the piano since I was about
eight. If my piano's been tuned, then I wasn't old enough to remember
it. I don't know how often a piano needs to be tuned, and I don't know
for sure that it's out of tune and that that's what the problem is.
Basically, my piano sounds different from other pianos. It's hard to
describe, just that every time I play a different piano, especially if
its for a competition or at a recital, though not as much at my piano
teacher's house, I just kinda jump. It sounds different. It makes me
freak out while I'm playing, lol. Basically other pianos just sound
more-mechanical, I guess? They almost sound like a friggin' keyboard
to me. And I doubt this has anything to do with it being tuned, but
other piano's keys are so springy, that that also makes me freak. A
lot of things do that-I haven't played a concert without screwing up
since seventh grade, and never screwed up before then...maybe it's
some late-developing stage fright...idk...I should fix that...but back
to the point. I get off topic a lot. Basically, my questions are: Do
you think that the problem is that my piano is out of tune? If so, how
much does it cost to get a piano tuned? And where could I get my piano
tuned.