I've been having mild chest pain for 8 hours now. should i go to the er?

Perhaps: It is not likely cardiac otherwise, you would not be writing this question. I would say you have gerd or gastritis. At your age. The chances of cardiac etiology is very low. Caridac pain causes nausea, vomiting, radiation to the neck, chin down the arms. Heaviness lasting sometimes less than one minute or even 30 seconds. You will feel impending doom. Have it checked out with your family doc.