Upper GI Series?

I went to the to doctor today because I have been experiencing stomach pains at the top of my stomach (feels like my stomach has to growl but can't.) Anyways my doctor ruled out acid reflux or a ulcer because I only get this maybe three times a week and occurs only in the afternoon strangly. She said I could have a hiatal hernia and I should get a Upper Gi series to test and find out (she also says it could be stress mostly but wants to make sure its nothing bad). I have done research so far on how the procedure is done, I am just wondering if the Barium stuff makes you gag or get sick when/before/after you drink it. Also if anything hurts throughout the procedure.