It sounds to me that you really do need to go to your Dr. and have a ful work-up. it could be something small or it could be serious, but if you are osing you balance and faling it is angerous to you and needs to be addressed before you really hurt yourself. I had similar problems and found that I have a serious disorder, so I suggest that you confide in your doctor and try to get to the bottom of it.
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Well, not all teenagers sleep much. If you are sleeping too much, collapse once in a while, then it would be worthwhile to rule out postural hypotension, hypoglycemia, anemia, PCOD, mitral valve prolapse in heart, and thyroid disorders.
Since I cannot examine you and know other related conditions you may be having, nor is a detailed history possible on net, I have listed the various possibilities that should be looked into. Please consult your PCP to run tests and examination to clinch a diagnosis.
You need to get to the urologist to make sure there is no electrical problems going on. This sounds scary. Don't put this off.