Alex,

Bonnie, Bruce, Don, and others are absolutely right - you MUST see a medical voice specialist RIGHT AWAY. You mention going back to your GP - ok, but not good enough! From your description, you are in serious danger of permanent damage, and YOU MUST SEE A LARYNGOLOGIST NOW.

For those looking to be scared straight about good vocal technique and the importance of prompt medical attention to these symptoms, I recommend video of vocal fold nodules.

It IS possible to belt safely. It's just that many people don't, because they don't really know how - there are lots of teachers and coaches out there who are doing more harm than good.

Best of luck,
Ken