mentally outgrowing everything?

I don't know what's been into me lately. For months ive been avoiding everything. And most of the time, im so over my friends, and anything that has to do with talking to people. I deleted all of my social networking and just been keeping to myself. I never wanna go out. I feel like all I want to do right now is get through my last year of high school and get on with my own life by myself. Im not depressed or "socially awkward". Im okay, I just don't know why I don't feel how I used to. Months ago you would of seen me posted on every social network, living life, and just having fun with my friends. but now.. I don't care to do any of that anymore. i don't intend to be selfish towards the ones close to me but my attitude is a very  "I don't care it's whatever" type of thing. 
is this normal? or could it possibly be a phase?