I've been playing in bands for about 8 years now. I play guitar and sing in one, and play drums and sing in the other. Recently when playing, I tend to get really light headed when I yell out or sing in a high register. This has happened at every show consistently for about two months. It never happened before that, and doesn't happen anywhere else except on stage.

I know this isnt WebMD, but maybe this has happened to someone else?
Breathe more.
dirtbag ballet by the bins down the alley
as i walk through the chalet of the shadow of death
everything that you've come to expect

I'm an experienced singer. I know how to properly breathe and have done countless shows singing. I've never had this problem before.
Moved to Singing & Vocals forum
But boys will be boys and girls have those eyes
that'll cut you to ribbons, sometimes
and all you can do is just wait by the moon
and bleed if it's what she says you ought to do