I would see a chiropractor, a good one will take some x-rays and work with you. I have had that feeling, and when I do, it is usually my ribs being "out" when he adjusts me, I am better again.
hi,, i had this same problem. it hurt right on the under wire of my bra and hurt wen i took a deep breath in. i didn't know what it was. i went to chiropractor and they did ultrasonic ultrasound.. something like that. . which is like a shocking thing they put on it. it helped a little they said it was PROBABLY a pinched rib. i didn't think it could be because if i pinched it i would have felt wen i did it. but that's what they said mine was. it just went away with time. good luck and god bless