HI,

Could be many things.

A suggestion would be to have a good assessment from a suitably qualified physiotherapist.

It might be a midback spine problem, ribs problem, nerve problem, muscle problem, referred pain from the neck or shoulder or lower back or shoulder blade or collarbone etc etc.

It also might be a lung problem or abdominal muscle problem, coordination problem, visceral problem, lower leg muscle problems etc etc.

It is very hard to tell without a good history. What you can do, what you can't do etc. As much as well all like to help, nothing at the moment beats seeing a client and feeling what is going on.

It has been a month now from what you say and it is affecting your everyday life (but thankfully no pain). Your symptoms are very common to what we all see everyday.

A simple assessment will cost you very little and can be of great benefit.

Good luck!