POTS is Postural Orthostatic Tachycardia Syndrome. It’s a form of dysautonomia (autonomic nervous system dysfunction). Way over-simplified, if your body can’t regulate your blood pressure as you move around, you either aren’t getting enough oxygen to cells (brain and other), or your body is over-working to compensate (e.g., increasing the heart rate, etc). It can cause symptoms like extreme fatigue, brain fog, exercise intolerance, headache, and more. Lots of times the symptoms are helped by lying down and being relatively still (which is no way to live obviously, but makes sense when you understand the mechanics of the condition). Fortunately I live close to Johns Hopkins (in Baltimore, MD, US), where there is a program that specializes in it, but lots of doctors don’t know about it or properly understand it, so it gets missed a lot. Awareness is increasing, partly because of research into long Covid (which seems to be connected/similar). There are specific tests they can do (e.g., tilt table) to confirm. Here are a couple links for basic info if you think it might be relevant to you: https://www.hopkinsmedicine.org/health/conditio... or https://www.potsuk.org/ or http://www.dysautonomiainternational.org/page.p...

Postural Orthostatic Tachycardia Syndrome (POTS)

https://www.hopkinsmedicine.org/health/conditions-and-diseases/postural-orthostatic-tachycardia-syndrome-pots

Dysautonomia International: Postural Orthostatic Tachycardia Syndrome

http://www.dysautonomiainternational.org/page.php?ID=30

Home - PoTS UK

https://www.potsuk.org/

What is POTS if you dont mind me asking. I hope you are recovering the best to be expected. You mention 4 operations which Id be interesting to hear as after 4 yrs of begging, my new gyno will consider it and am getting MRI for planned AI surgery next year.
Thinking of you