I have tmj, and have been experiencing nausea and vomiting a few times a month for the past six months. can tmj cause nausea and vomiting?

Not likely: TMJ or TMD does not present with these symptoms. Pain within or around the joint with or without popping and/or grinding , inability to open or chew, muscle tension and pain in the muscles involved with opening/closing of the jaw and even the head/neck, with/without malocclusion are the most common symptoms. I suppose if any of these symptoms were bad enough then nausea/vomiting could occur.