i feel so frustrated!!!!

by bf is convinced that it's his fault i'm depressed. it's impossible for him to understand the difference between "sad" and "depressed". my anxiety is through the roof. how can i tell him that this is like a big wound inside me, not anything he could cause, that it's been with me for years and years? how can i make him understand that it's not him that drives my want to SI (which i haven't done in 2 years but i admitted to him i've been thinking about it often)? urgh. thoughts? advice? help.