Struggling with Chronic Illness and Lack of Treatment

Hi, I am new to the app. Sorry for the long post/rant. I have confirmed diagnoses of Constrictive Pericarditis, POTs, MCAS, Chronic Costochrondritis and hypermobility. Its taken me 5 years to get these diagnoses. It feels as if as soon as I got diagnosed with these conditions by the consultants I was pushed back to my GP. No treatment plan, no steps forward and no future plan. Talking to my GP about the fact the tablets/treatments I am on aren't working is like talking to a brick wall. They either say they don't have the knowledge to do anything and will need to refer me back but as I have a diagnosis it might take a while. Or worse they say "Oh its 'health anxiety' or depression and that my conditions/symptoms just require therapy to treatment them" or " I'm young it will pass". Whilst I do appreciate that health anxiety is a real thing and possibly a factor, the only reason I have health anxiety is because no one seems to be listening or treating my very real conditions and symptoms. My whole life has changed so yes I am depressed/anxious but my tachcardia, hypotension, allergic reactions and passing out aren't a figment of my imagination. I have been unable to work due to passing out and prolonged illnesses. I am scared I will lose my job if I cannot get my long term conditions under control. The worst thing is the treatment for POTs could be making my Pericarditis worse and the Pericarditis treatment could making the POTs worse. I feel like I am in a constant negative feedback loop with no end in sight and the people who are suppose to throw me a lifeline have cut it up with scissors. I honestly don't know what to do.