Re: should i
First, happy (almost) birthday! And good for you for wanting to take care of yourself and begin working out. I think this is a good idea.
Second, there's absolutley no truth whatsoever that working out will stunt your growth or otherwise be detrimental. to your body (or to puberty). Actually, the opposite is true. Your body will be healthier, and it will perform to it's best. The really important thing to remember is to not overdo it, start slowly, build gradually. A little time consistently and regularly will do the job nicely, this will take time. Don't try in a rush to get it all done in one or two visits, you'll be disappointed and in much pain! Consider asking one of the trainers at the gym for some suggestions, too.