Please get it checked out by seeing a doctor! (Don’t rely upon the coffee room for medical opinions; I’m not a doctor but I play one on the Internet.)
GERD is not limited to acid reflux/heartburn. You should get a medical checkup. There are changes in the nerves that can occur which can resemble the symptoms you describe without feeling the classic heartburn. Other illnesses, like diabetes, can also cause changes that make you feel nauseous and/or like you have a lump in your throat. If you are experiencing anxiety or stress, that can be a trigger, too. There are medications that can prevent this from becoming full-fledged GERD. Hatzlachah.