Help, im choking on phlegm!?

i am 12 yrs old and my throat is coated in phlegm. every time i try to cough it out i choke on it and get scared. i dont wanna choke anymore:[ i am basically whispering b.c if i talk it gets stuck up there again. please help me:[ choking is my biggest fear:[ i also have a singing competition THIS FRIDAY! and it is tuesday so if i dont get better i will be crushed if i cant sing:[ please help! :[[[[[