Sometimes these things are difficult, and GP's do only deal with general medicine. Most are far from being specialists in a specific area and look at what is presented to them. Based off my experiences, if at the specific time they see you they see no actual symptom then they may take a view there is nothing to work with (I've met with non-action many times).
I went to my GP saying I was experiencing bad side effects when on a previous medication - the specific random doctor I spoke to did not want to know! Some days/weeks later (I forget) I had to call an ambulance due to experiencing tachycardia with my pulse rising to 135. I spent 12 hours in A&E being checked over, but I did get my meds changed, so I guess it was worth it.
So I understand the stress of this, and the stress of trying to actually see a doctor in person, let alone one which will look further. Has your gp referred you to the hospital for any tests?
I had various scans and a 24 hour heart monitor before I was prescribed the beta blocker (apparently my heart is fine, it just wants to do me in with it's abnormal rhythms 🙄). In May this year I had a 48 hr heart monitor from the hospital but am still waiting for results / follow up.
It may help to ensure before you see the doctor you put things down in writing so you can highlight issues, just key stuff - short points which can be discussed further. Hopefully you get a doctor who can both listen and talk, I find those are rare these days.