Im 40 years old, male, in average - good health, regularly went to the gym up until 8-10 months ago, lower back injury has stopped me going.
In the last two weeks I have been waking every 3/4 days or so with a dull ache in center of my chest after 6/7 hours sleep, once up it goes after a couple of minutes, after hot shower, stretching etc. I have no shortness of breathe, no other pain during any other time of the day. no other medical issues, any advice/help?

ps. Im seeing my doctor soon, but would like some feedback if anyone knows of what this is possibly a sympton of or has experienced a similar problem? Many thanks