Murmaration I have been through your last paragraph so many times. I've lost count of the number of times I've questioned if everyone else actually feels like this but I am just a wimp. 
I have had health professionals tell me there was nothing wrong, it was all in my head, it was anxiety, hormonal - you name it, I've had it thrown at me. Finally being diagnosed with POTs via a positive tilt table test and full medical history, plus active stand test, while not actually fixing anything, yet, has at least stopped me constantly questioning myself and finally meant that my GP is taking it seriously and my family don't have any doubts anymore either.
I'm currently off medication, as the first bb they tried me on was dire in terms of side-effects and I waiting to start ivabradine, once my GP has received the letter from my cardiologist. I am off for an echo at the end of the month, as my mum has dilated aorta and I have had a couple of funny ecgs and some arrhythmia.
My mum is going through something very similar. She was referred to cardiology 18 months ago for breathing issues and chest pain. They did an angio, said no issues, but triggered two tia's.
She was then sent to General Medicine as a follow up to her tia's and the GM consultant went ballistic that no-one had done and echo. Echo was done and she was found to have severely enlarged left atria and dilated aorta.
That was almost two months ago, the letter never arrived at her GPs, so GP was unable to discuss the results when Mum when to see them and no-one has followed up on those results.
In addition, she is currently going through a really bad rheumatoid arthritis flare - I have never seen her in so much pain, despite being turned away from Rheumatology who told her she doesn't have RA. She absolutely does and this flare has her hands crippled with massive nodules.
She's now going back to Rheums to be referred on for an EDS diagnosis (little doubt she has it, she's text book and the echo report suggested it as the probably cause of her aortic dilation) and we're hoping they finally dx the RA as well.
The arrogance of some medical professionals, that causes them to just dismiss people who are clearly ill, without proper investigation, is astounding and frankly beyond unethical. 