Hi,
Your rabbit has an ailment called Torticollis which you can see here:
http://www.bio.miami.edu/hare/tilt.html
http://www.peteducation.com/article.cfm?cls=18&cat=1803&articleid=2371
http://www.rabbit.org/journal/3-8/head-tilt.html
It is usually caused by an ear infection and upsets his equilibrium like our motion sickness.
He will have to be seen tomorrow for an antibiotic.
In the meantime add plain pedialyte to his water. Take him in a seamy bathroom where you ,have run a hot shower to break up congestion.
Keep him as calm and quiet as possible.
Please let me know how he is.
I hope he feels better very soon.
Best wishes,
Terri
Feline Healthcare Expert
Expert in feline health and behavior. 20 years experience with cats.