I am bulimic what should i do?

my sister called me fat so i went to the washroom and threw up i did this once a day for a week i researched what i was doing and i realized how serious this is i stopped right away but i told some of my best friends and they were all very concerned one of them started to cry i will never throw up on purpose again and i regret but what should i do to prove to my friends that i will never do it again?