You have to overcome this problem you describe. Eating, combined with time, is the number one component of gaining weight.
If your meal plan covers buffets / all you can eat, then you need to make going to those part of your day- more important than lifting. Eat as much as you can handle, then buy stuff that you can eat in between classes or back in your room, like cans of tuna, cups of yogurt, chicken sandwhiches and/or sausage biscuits, for example (which are good cold, imo). Basically, you need stuff that's easy/convenient to eat, since you are not much of an eater right now. Also, you need to keep eating as much as you can and over time you will be able to eat more and more as your body gets used to it.
Your split and exercise selection matters, just not nearly as much as increasing your appetite and caloric intake.