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.