Teenage depression, i need help serious answers please!!?

Okay, im 14, as of the 22nd, and i live what some would call a decent life, Girlfriend, good mates, its just i have a few problems going on which i'd rather not say as my friends know im writing this. But i always feel suicidal and i am currently o nthe brink of purging after 4 weeks of resisting it, please help me!