Feeling of lethargy and illness after long haul flights?

Hi there, I have just returned from a year overseas. My last leg of the journey was a long one and took about 30 hrs flying and airport transfers. Since returning I have been feeling pretty ill. Tired all the time and my ears feel uncomfortable and sort of motion sickness’y. I feel sort of like being hungover without ever having had a drink. Has anyone else had this or know what causes it? I had thought it was just being worn out by the flights but I have been taking it fairly easy for 4 days and I still feel like hell. Will it wear off? Its not actually debilitating but it is pretty horrible.