I would say, do not underestimate the stress of such a huge relocation, along with the stress of starting a new PhD programme. I am in the start of my second week in a new country, and I think it is just going to take several weeks before things ease into "normal", that it takes some time to make all the adjustments. I find that indulging my odd cravings for things from home ( like Doritos and Mcdonalds--that I never ate at home!) from time to time, remembering to laugh, a lot, and getting the right amounts of sleep and exercise, and eating properly make a huge difference. I have finally caught up on sleep, and the world looks completely different!