Thanks @argueifnecessary in my rational moments I can accept that it's probably to do with Pots or some other non-serious condition. In fact I can rationally accept that it's most likely to be caused by anxiety and stress!
But then the emotional reaction kicks in and I think and behave as if I definitely have a terminal illness. Especially now I realise I have had an eye twitching for a week as well. Clearly a brain tumour or degenerative disease!
12 days until my GP appointment and test results, seems such a long time to wait.
So far this year I have, in my mind, had a lung tumour/covid damage in my lungs (tight and heavy chest, now gone), some kind of blood clot or scary lung or sinus disease (coughing up horrible reddy brown mucus, now cleared up), breast cancer (I have cystic breasts so lots of lumps), melanoma (bleeding and scabby mole that I later realised I had itched, now fine) heart failure (racing heart, which I still have but feel less panicky about and have managed to go on a few runs with DH without dying), sinus cancer or growth in my nose (sinus pressure, which was awful yesterday and seems to be gone today), brain tumour (dizziness/vertigo, still not sure what is causing it) and now Parkinsons/AML/MS/brain tumour again (twitching and vibrating abdominal muscles and twitchy eye).
It's so exhausting. CBT isn't helping at all as it seems to be focused on accepting that there is a low risk of a health issue being something serious, and much more likely to be either normal or minor. I already know that! The problem is not being able to cope or stop obsessing about the maybe 1% chance that it is something serious. CBT doesn't seem to help with that!
My therapist thinks I have PTSD as I was ill when pregnant and the doctors/midwives fobbed me off all the time saying it was just anxiety and there was nothing wrong but it turned out to be serious and my DC nearly died and has been left with a lifelong disability. Probably a 0.001% chance of it happening. But it means that a 1% chance of something dreadful happening is of no comfort to me, and I feel like I am the only one who is responsible for my health and figuring out what is wrong as the doctors got it so wrong before so I can't trust them.
The only thing that seems to help is hypnotherapy (free on YouTube) and keeping busy.