Hello Hay, and welcome to the boards!
I have had gerds for about 6 months. I also get a "fluttering" sensation. I think it is my diaphragm that may be having a tiny flutter or small spasm. I am not sure if that is what you are experiencing, but that is the only way that I can describe it.
I also have other symptoms such as lump in throat feeling, frequent burping, heartburn and esophageal spasms.
If you read this board you will find many symptoms that we all share, some more common than others. Whenever I get to feeling really depressed or overly concerned, and I read that others have similiar symptoms, it does make me feel better.
As far as your medication goes....Some people need to change meds if the first one isnt working. But you must give it at least 2-3 weeks to even start feeling the slightest bit better. For me, I felt a bit better after a few weeks, but I didnt really start feeling better until about 4 months. I have had this for about 6-7 months now, and most days I feel pretty good. I dont know if I will ever feel quite "normal" again, but I do have days where I can almost forget about this. It can take a long time, so dont lose hope!