I have a heavy chest sometimes. It's not painful, it just feels like someone is sitting on my chest. I know due to covid noone wants to go anywhere but perhaps a trip to the ER would be appropriate. But Your doctor should work with you to see you or at least have an over the phone appointment with you. I can't see them rejecting all patients they probably just aren't doing routine check up appointments.
Your exhaustion could be due to the anxiety you've been experiencing because of your shortness of breath. When I'm anxious, it exhausts me.

Somewhat, the left part of my chest feels tight and I do have abdominal pain, which is all apparently leading to GERD. The medication was working but after recent stresses, things have deteriorated again!