My vocal chords are hurting so bad!?

Okay, so I need a professional's opinion. When I sing with my choral voice, I can't even make it through one verse in a song without my throat hurting, particularly the left side. However, when I'm belting (like in show choir or in theatre), there is no pain. I can belt higher than I can sing chorally, and trying to sing high sounds both airy, and BAD. Like a boy in puberty or something. I've tried more support, more water, breathing exercises... nothing has been working... and i'm really afraid that my voice is going to SUCK for my upcoming production.... help?