You are brave for reaching out. I do think many parents (maybe even me) might tell you to try to stick it out, that a girlfriend is one important part of life, but maybe not something to sacrifice other parts of your life for at this age. But…you are clearly suffering, if your appetite and motivation are so effected, and you have reached out for help. If you’re not functioning in your school (where I’m sure you are paying $$$$), it doesn’t make sense to stay there if you can’t work it out. But…it’s only been two weeks. You are still in transition time.
Many, many high school couples maintain their relationship when one or both are at college. Three hours isn’t really far away; it’s drivable in one day and definitely for a weekend! Not that I think you should come home every weekend or have her come every weekend…that won’t help you make changes at school (friendships, relationships, activities). You have to find some new connections to take your mind off your far away girlfriend. And maybe make a plan to see her once a month or so.
There are many threads on the boards about people in your situation right now…new at school and lonely. Search for those you’ll find lots of great tips and success stories.