You'll definitly grow taller and put on some weight as you age, unless your genetics don't allow it. Find anything you can to workout, and make sure you do it the right way.
Also look at articles in here: Rosstraining.com
He give alot of exercises you can do with all types of things you can find anywhere. If you have a tree, get a rope and climb up the tree, do rope pull-ups.
After getting the rope tie it to a piece of wood or metal and put stuf on it, then pull, pull, pull.
These are all seen on the website above and all very helpful.
You are blessed by the hand of your free chosen god