Please rethink skipping exams, school or work for anyone. Girlfriend's that care would not let you do that. It is not necessary to risk your future to have a girlfriend. You don't need to be that desperate honey. When a relationship is "right" then your education, or work, is a very high priority for them too, and they will support you by being available to visit you while you keep your commitments. Don't worry, you'll be in a good relationship some day, don't waste too much time on a relationship that is so confusing and disjointed. You don't have too, the right thing will come along.
I guess I'm confused why you are in this relationship. From what you are saying it sounds like your girlfriend does not want to spend much time with you. If you are sacrificing yourself in many ways to be with her, then you are going to feel sacrificed in this relationship. My advice is to reach out and make an effort to spend time with her when it feels good to you and if she still isn't responding by spending time with you then maybe you will want to think about if this is the relationship for you.