Within the last couple days I have been experiencing some breathing problems that are beginning to worry me a little bit. When playing runs up to C above the staff I get extremely light headed and feel extremely dizzy. I never used to have issues before with light headed-ness or anything of that nature, and the problem only started occurring within the last couple days. When playing higher parts I always breath in fully from the bottom up and blow the air with pressure from the abdomen. I don't see how this problem could really result from lack of air as I'm taking full breaths and the lines I'm playing are not very long at all. Does anyone have an suggestions or theories as to why this is happening? Am I being too tense around the neck or shoulder area? I'm using the breathing techniques recommended by Bobby Shew for the higher parts but I'm still getting the light headed feeling. I try to relax but this doesn't seem to help much. I would really like to fix this problem and would appreciate any advice to rectify it. I appreciate the help!