how often should i wash my face, i havent done so in 4 months?

Face washing is a very important part of your annual shower.

you should clean it with water at least once a day to get rid of germs and bacteria because your mouth and nose are on your face and a lot of infectious disease transfer through the mouth and nose.
if you haven't seen any skin problems, I guess you have showered in the last 4 months so the cleaning involved is good enough for your skin

You're supposed to wash your face every morning when you wake up. All that oil that has built up in 4 months, eww...that's messed up! No offense, wash your face every morning!