I Am Not Sure What To Do. My Son Is

I am not sure what to do. My son is on the Autistic Spectrum. For the last few months if I get mad or raise my voice at my sons sister he gets worked up/nervous to the point of throwing up, He says he gets nervous because I get mad or upset and he just wants me to be happy. I feel so frustrated as I am of course going to get mad at times. Any suggestions. A sad and frustrated mom. HELP! I don't want my son to throw up but I am human and anger, frustration, getting upset is normal.