Some homesickness is to be expected, home-college IS on of life’s most difficult and abrupt transitions for a lot of people. Lots of students also get an end-of-summer seasonal depression. Couple these two and things aren’t good.
Being shy/crying/not partying isn’t really a huge deal, you’ll get through that. However the eating thing is a problem. Stick with a regular diet/meal intervals or you’re liable to end up obese later in life and get diabetes.
I would give it a week, see if you feel better. If not, go see a therapist and get some Prozac.