am i getting old before my time??

i know i've mentioned this a couple of times now but it's starting to become a super huge fear, i don't wanna be too old for my age..at work people are commenting on how mature i am and they're all shocked when i tell them i'm twenteen (yes i typed it right..TEEN..there is NO way i'm leaving my teen years behind, what excuse would i have for my poor behaviour then?!) i'm getting proper worried that i'm too old :( i don't like it..as kids we kept a lot of adult company and i aspired to being a grown up, we had to be very mature at times and i feel liek kids nowadays don't get chance to be kids for very long, the age of innocence is dropping every year! i've lived indipendantly of my perents since the age of 16 me and my two sisters (aged 18and 19 at the time) decided we didin't wanna move to france when they did so we got a flat together..ok so a lot of responsibilty required but does it make a person age and become boring?? i hope not! i have to throw this question out and any comments greatly appreciated coz i like to think i'm the sort of person who's fun loving etc etc not slippers and a night in!!
ok so the other day i told my chap i fancied us getting away for the weekend together..we both have stressy lives for quite different reasons and so i thought it'd be good to go to somewhere like center parks for a spa weekend to unwind, get away from it all without having to travel too far, have somewhere quiet where we can concentrate on one another and then we could come back refreshed..i thought it'd be good coz we wouldn't have to go too far, they're not too expensive and we could just chill...he humoured me, listened to my suggestion then later replied with that's what old people do!! i nearly died! my romantic thoughts had been put on a par with geriatric nursing home retreats! i was gutted to the core, is this what i'm becoming?? ok so i'm not totally wreckless all the time and yes there were practical reasons in my thinking with the holiday but i didn't think it was gonna get that response. he said holidays are all about getting drunk and falling over..i laughed at first but then realised that's not my scene..don't get me wrong, when i've been paid you won't catch m,e in the house, i'll be out every night with different friends going to a club, to our local, cinema, random drives in the night i love living and i love spontineity but the way things are for us at the mo i don't think our circumstances afford us such a luxury..maybe i'm a realist and at my age you're still supposed to be an idealist..it's just i've been let down so much over this last year that for damage limitaion sake i'm avoiding stuff that hurts me, is it that the only way to have fun is to play with fire?? or is it too grown up to be asking that right now?