"hollow" Pain Near Bottom of Rib Cage

I have noticed that when I do semi-strenuous exercise, i'll get a horrible pain in my right side, which feels like it's either near the bottom of my rib cage, or just below it. The pain feels very "hollow", as if there was a hole in my ribs that air was being pushed out of.

I get a dry, cold feeling in my mouth when this happens, and it will usually hurt badly to breathe for a little while.

Not very long ago, I was rather hyper and I was dancing around to some music. It obviously wasn't excruciating work - I was being silly and jumping around and doing hip and arm movements and such. But I had to stop after about 15-20 minutes because I got that hollow pain. The pain lasted for about 10 minutes.

When i'm in gym class and I have to do laps, I get this hollow pain, and sometimes I can't breathe. When I run the mile, I can't catch my breath for a very long time, and the pain in my side (sometimes it spreads to my left side) doesn't recede for a long, long while.

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I admit I hardly exercise - walking up and down some stairs and walking the dog is about it. My lack of activity probably is the cause of my intolerance to actual exercise.

I used to do some low-degree aerobics for about 20 minutes once every day, but I would be in so much pain afterwards that I couldn't. And the next day I was still in pain, so I had a harder time doing the exercises. Eventually it got to a point where 17 minutes was extended to an hour from pausing.

But what do you guys think? What could be causing this pain?

If it helps at all, i'm 5' 4" and i'm guessing I weigh a flabby 150 pounds (down from 204 two years ago!).

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Scaredbaka - is lazy