I guess you have to admit that if you fly control line stunt you must be a little bit unbalanced....
So, here's an exercise that should help. Please be careful doing it, so you don't add a broken arm or something else to what you already have...
Standing with your feet together and your back to a wall, hands and arms held to your chest, elbows bent and pointing straight down, with your hands closed into fists and held at your collarbones and under your chin (this is mostly just to keep your arms out of the way):
1) bend straight forward so your chest is pretty much horizontal (like you are bowing and make sure you have given yourself enough room so you don't bonk your head on a table of chair or wall),
2) rotate to your right from your waste, still bowing(your torso will be twisted - and yes, this will stretch the muscles, so be careful not to pull anything!),
3) straighten up, still facing to your right,
4) now, rotate your waste so you face forward.
5) repeat for the left side.
6) reverse direction, that is, turn to your right side, bow to your right side, rotate forward still bowing and then straighten up.
7) reverse direction to your left side.
8) try to stand perfectly still and maintain your balance
Again, please be careful where you do this so you don't fall onto something (including a cement floor!)and maim yourself! Do it in repetitions and then try to stand perfectly still without losing your balance.
Okay, practice it a couple of times a day until you can do it!
Got it? Great!
Now do it with your eyes closed!!! Please have someone "spot" you so you don't fall and kill yourself doing this!! As you get better at it, mix up the directions and the reversals and then try to stand perfectly still with your eyes closed.
If you can do this and still have balance problems at the field...well, I guess it is time to see the doctor.
Good luck and remember that this is a learned skill, so if there isn't anything wrong with your inner ear you should be able to do this and imnprove your balance. But again, it will take a small investment in time, but a big investment in consistancy as you need to do it regularly if you want to see improvement.
Scott