Chiropractor

I'm 14w5d and have been recently going to the chiropractor (I'm a cna & since I've been pregnant I've been experiencing a lot of back pain). My doctor has been putting me on a lumbar massage bed (I spend about 10 minutes on it while it rolls all the kinks out of my back/hips) the past few visits after my adjustments, but this time around, the massage bed made me extremely nauseous. It's never happened before, but I was wondering, has this happened to anyone else? Any ideas as to why all of a sudden it's making me nauseous?