Maybe a little of both...Relationships can still survive on only seeing each other a couple of days a week. And, as they say "absence makes the heart grow fonder." Maybe he's just having a bad week. The best thing I can recommend, since you two have been together for two years, is that you come right out and tell him what's bothering you. It can't be as bad as you imagine. You've been off school, but he still has his hands full with studies, and maybe he's been stressed. He was sick there for a while. Don't get upset until you hear both sides of the story...

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It is impossible to love and be wise
-Francis Bacon