Hello~It could be a pinched nerve due to some vertebrae in your upper back that is out of alignment, possibly seeing either a physical therapist, Osteopath or chiropractor might help, also, some stretches.
Another thought that comes to mind is it could be heart related. I don't want to alarm you, but some of the symptoms can be related to heart issues. You are fairly young still, but heart issues can be no respecter of age or person, and sometimes folks as young as their twenties can have them.
If it doesn't get better, then I would see your GP, he will be able to determine what is going on and will be able to prescribe the needed tests.