Open Question: I do not like motion sickness. (Only on car rides)?

I get motion sickness when I have some food in my body ( ONLY ON LONG TRIPS ). I throw up the food sometimes and then I feel all better. Is this normal? If I don't have food in my body, I just burp. I think it's just the air. Sometimes I keep my mouth open, but not all the time, and I still burp/barf. Is there any way to stop the burping and barfing, because I get a headache and my stomach