there is a lot of things going on in your response. i used to be JUST like you. evidently, you ARE doing something wrong. it seems that you inconsistancies are getting the best of your body.
what you need is a routine. once i got that down (and i am in school as well) my body responded dramatically. i went from being 130 to 170 within the course of 8 months.
eating is not as easy as everyone on this board may make it. you need to eat the right things at the right times with the right drinks and have the right workout routines. understand this and it may throw you for a loop - you body does not grow from your food directly, it grows from you bodys hormonal response to the food and muscle stimulation (ie working out).
it seems you are stressed, inconsistant, and uneducated - all these things combine to make for a body that wont grow.
you need to evaluate your "routine" and write it back to the board, give us your stats, you goals for the future, workout history, what happend to your back?, what supps you take, etc etc
then we can help you evaluate the situation and understand that "less is more" and eating the RIGHT way will make a huge difference.
Finally, understand that shakes and supps are NOT what help you grow they aid in your growth. FOOD is the number one thing you need to worry about right now, so even eating a full breakfast every morning will make a big difference in your body's composition.
MM