I've had this on and off for about three years (so I'm assuming it's not life-threatening, even though it feels like it sometimes!). And I've been to several doctors and had a plethora of medical tests - all normal. In addition to all my other weird symptoms (foggy-head, vibrations, tingling, neck stiffness, hot flashes, etc.), almost every day I have a pain/pressure/tightness feeling in my chest, located beneath the sternum, like in the center of my breasts but down a couple inches. I keep thinking it's my diaphragm or something wrong with a bone in that area or a vital organ. It often feels like I can't get a deep breath and very suffocating. Sometimes, it's so severe that the sensation runs all the way up my neck to behind my ears! Feels like someone is strangling me. Yet, all my tests came back flawless?!? Well, I do not FEEL flawless! 
Please help me... Does anyone else suffer through this? Have you found anything that helps? Do you think there really is something wrong or is it just anxiety?
P.S. One test that I took (GI series, barium swallow - yuck!) did show that I have "mild to moderate GERD/acid reflux," but the GI doctor said that it wouldn't be causing myself symptoms. I have no burning or heartburn at all, and it doesn't just happen after I eat - it happens on and off whenever! I did try Zantac (acid reflux OTC med) for two weeks, just to see if it would help. It did not. It seems to feel a little better when I massage the area, stretch, lie down flat or lean forward. What the HECK IS THIS???
Hi, Shea.

I know you posted this several years ago, but I was wondering if you've had any more luck verifying the cause? Everything I bolded in your post applies to me. I've gotten these "attacks" after a great deal of physical stress for a few years now, but just in the past few days they've been so bad I went to the ER twice, and they were
not caused by any apparent stress. It really does feel like you're dying, especially because I also get really faint -- I almost passed out twice. Like you, the ER docs couldn't find a cause, and my regular doctor is sending me to a GI specialist (I haven't gone yet).
The thing is, I'm only posting because I found this thread in a Google search for "pain below sternum". I didn't even notice right away that the forum is for anxiety. I've never had anxiety or panic attacks. My symptoms only flared up after extreme
physical stress, not emotional. A lot of things people have posted make a lot of sense...for someone with known anxiety. I was wondering if anyone knows whether these symptoms could be caused by physical stress, instead of emotional stress?
See, I also have chronic Lyme disease, so I suppose it's possible that the disease is causing everything. But I've had it for 10 years, and this latest string of attacks (3 in the past few days) came out of nowhere. My Lyme is hard enough to handle...as it is, I can't go to college, get a job, or even drive a car. I can barely do everyday things around the house...and if I had to deal with this new set of symptoms regularly... Crap, I just don't know.

If anyone could shed any light on anything I've said, I'd really appreciate it.