I don't know what category this would fall under. I don't feel any pain but the butterfly sensation is strange. The doctor I saw a few years ago about this said that he thought that when I sleep at night my chest in on a down position and that the change to standing up in the morning can give me that sensation. But it only happens on the right side. It almost feels like it's on the outside of my right lung, not in the center, right by my ribs. A few years ago I was on the floor playing with my baby when the phone rang, when I jumped up to answer the phone I must have snapped or jerked my back because something dropped me to the ground in severe pain, like I just pulled all of my muscles on the right side of my back. Wow, the pain was something, and it was muscular. I never went to the doctor because it was muscular, but the pain lasted a good couple of years. Could this fluttering be because of that?