I eat a lot (and a variety) of foods and don't excersise (only walking, lifting, ect). It's almost impossible for me to put on weight, or get to anything above 120. Could there be something wrong with me? Stress? Or am I just getting too many "empty calories"?

You don't really give enough information. What is your age, how much are you actually eating, what is your lifestyle? Walking and lifting are exercise too.

Empty calories are more likely to put on weight than stop you gaining. Chances are you are eating the right amount for your body, and just can't force yourself to eat more.