i feel like i dont exist, what is wrong with me?

ok im 18 im a senior in high school and ive had pretty bad depression (a psychologist affirmed i had it) since roughly beginning of junior year (from what i can tell what friends have said and journals). i did a drug called salvia over my junior-going-onto-senior summer and it gave me alot of wierd effects. it made me hear voices and i self mutilated. i went through an 8 month period of heavy medication (primarily risperidol and lamictol) and i finally got off them because i was tired of not being able to get a *****. i can say with sincerity that most of the serious depression HAS left but what i am stuck with now is like a feeling of not existing. it started decemeber of 2009 and when i never thought it could get worse it, it would get worse. i have such a hard time just feeling there. thats the only word for it. when someone asks what i did for the weekend i have to sit down and think for 30 seconds straight 'wtf did i do' or when i do homework and stuff, barely can concentrate. thinking, reading, and memorizing all seem super distant. you guys reading this cannot understand the confusion and misery this not exist feeling is like for me. im supposed to be happy, im goin to college and i have tons of friends who publicly announce their love for me but i cant even feel myself. oh and for the past i wanna say 3 weeks, on every saturday night i have smoked weed with a friend. i dont think its doing anything wrong for me but i should say it anyways.

please guys i need a possible diagnosis or some sorta action i can take. PLEASE its ruining my life

thank you all