Why do i get so nervous when asked to read in school?

whenever i have to read anything out loud in cl (eg. homework, a short, paragraph, anthing!) i just get really nervous. i dont know why. for 9 years of my whole life i would read perfectly fine. this year when ever i am told to read my heart starts to beat like crazy and the words wont come out because i cant breathe like i try to breathe slow but it doesent work so i have to read one word then take a huge breath and read another and it sounds all shaky. the thing is i dont care whart my cl think of me im not scared of them laughing at me or anything and i tell myself this whenever i have to read so i dont know why it happens! i know this is a stupid thing to be worrying about and i shouldnt even get this nervous. its also strange because i can perform on the piano and sing no problem in front of the cl. youd think that wouldd be harder to do! so any advice how to not get so breathless that i sound like the guy in the wheelchair in malcolm in the middle! or any advice why this happens to me. i only get it ever since i eded up being bulimic:( do you think that may have messed up my nervous system?