Sudden Nausea as I fall asleep...

For a year now I have been plagued by nausea that accompanies the onset of sleep. I can go to bed feeling perfectly normal, no anxiety, no nausea, nothing. Then as soon as I drift off I am jolted awake by a pang of nausea. Over and over and over.

Has anyone experienced this before? My doctors have no idea what to do with me...