What Causes Migraines, Fluttering And Thumping Sensation In Chest?

I am a 50 year old woman and have been having a fluttering and sometimes thumping sensation in my chest for the past 3 weeks, more in the middle and right side than over my heart, followed by a need to take a deep breath. This happens at rest when I have been sitting still for about 30 minutes. I have cut right down on caffeine (from one cup of coffee a day to a smaller, milky cup of half-caf) but this did not make the fluttering episodes go away. 2 weeks ago I almost blacked out while singing and playing piano. I stopped singing and it went away, so I didn t think much of it, but then a week ago I passed out while hiking. It was a very steep climb but very short in duration - I passed out for a few seconds and felt better when I came to and finished the climb with no problem. I had a migraine headache for the next 18 hours after that, and I don t generally get migraines. I don t have any new stressors in my life at the moment -- everything is going along pretty normally. my heart was thoroughly checked last year when I had chest pain and ended up in the ER (it turned out to be costochondritis), so I know my heart is in excellent shape. I am also having a pinching pain that feels like it is in my abdomen wall to the left of my belly-button. My doctor checked me for a hernia, since I had an umbilical hernia repair with mesh about 10 years ago, but he said he couldn t feel any hernia. Any idea what this could be?