there are alot of answers but these are the fastest and best ways i know use the bathroom it won't always work but it usually does, and if it doesnt, see if you have a fever or need to vomit stretch...
if the stomach ache is in the abdominal area then u could just be having period pains or just about to start one. it could also be food poisoning, eating too much or even eating too little.
I have a car sickness all the time and these things helpChewing mint gumwearing Sea Bandseat little sugar before handstay away from heatlittle noise Hope that helps!