I had a really hard time in my highschool choir (junior and senior year), and to this day, after having become bulimic at the end of middle school. Although I made it into the audition only (top) choir at my highschool, I struggled more than anybody. Not because of the quality of my voice, but because of my lung and chest power. Through purging I damaged many of the muscles in my chest. It hurts when I breathe properly for singing and it also hurts when I fill my lungs completely or take quick full breaths. It also makes exercising hard because it hurts to breath heavily.

Try to take care. I don't know how much it can affect voice quality, but I know it can have a dramatic effect on breathing for singing.

Good Luck