Why do I get feel nauseous when im outside, when i feel fine at home?

For about a week now i’ve been feeling nauseous ONLY in public. Other wise i feel fine at home. I’ve had a history of GERD (gastro esophageal reflux disease) and i went to the doctors a couple days ago. The doctor gave me some medication for gerd, but he wasn’t so sure of what i had. He then recommended me to a gastrologist but i dont meet him until 3 weeks later. Im currently in the 8th grade and i went home sick twice in a row now. At school i feel severe nausea and somtimes my hands start to shake, but when i get home i feel fine. I’m not sure what’s causing this… i think it could be anxiety because i really really REALLLY hate puking and im afraid of puking in public. I think this mainly started when i went to a high school orientation. I got extreamally nauseas and i practically could feel something in my throat so i had to run to the bathroom. In the bathroom i burped a couple times but i still felt bad. Eventually the orientation ended and i felt fine. After this experience I’ve been feeling nauseous every time i go into the pubic. Can some body please tell me whats going on D:! is it anxiety? a phobia? or somethings wrong with my stomach. i really need to get back to school as soon as possible so i won’t fall behind >.<!