Not being a Dr or medical professional it is hard to say as it can be so many things including GERD, but, even a Dr that reads this can not say for certain, u really need to go in to ur Dr/GI dr for a full exam and give all ur medical history as recent meds can play a role in this as well.
Call ur Dr and do post an update on ur progress : )
If it is stomach only, it could be helicobacter pylori. If it is from the small intestine (gas pressure in the small intestine tends to lift up the stomach, which leads to nausea), it could be enterobiasis. Since you are a nurse you can get in contact with those buggers quite easily, especially if you are either in a geriatric or pediatric ward.