Anemia or Dysautonomia?

Hi all! Long post, sorry.

I (29f) suffer from endometriosis, so I already have chronic pain that I cannot explain, but when my joints started to hurt and I began to feel dizzy all the time, I went back to my doctors and they ran all sorts of tests. Everything came back fine except for my Vitamin D.

Took the vitamins, everything was fine, but I still had symptoms. Went to the cardiologist, they ran an adrenaline test on me and told me my blood pressure pluments during stress. Told to up my electrolytes and to drink lots of water.

Fast forward a while later, run more tests, see new cardiologist, and that cardiologist told me the reason I am sick is because I'm fat and don't exercise... While it is true that I am severely overweight, I ONLY GAINED the weight because I couldn't go out on runs anymore (I ran 1.5 miles daily with my dog) because I kept fainting. He said it was not possible, told me it was my weight and lack of exercise that caused this, and left it at that.

Went to a neurologist after that, told me I was fine, and then sent back to my primary.

Yesterday I went back to the doctor and was told to stop using a wheelchair. A wheelchair THEY RECOMMENDED ME TO USE, because I was becoming deconditioned. I explained that my legs are insanely heavy, that they've been heavy for years and are to the point that they're unbearable to walk on due to pain, but they insisted they could get me back on my feet in physical therapy...the same physical therapy that I was kicked out of because of my blood pressure issues...

That became a whole other issue where I had to explain, once again, that I faint often. Laughing triggers a fainting spell. Eating triggers a fainting spell. Coughing, sneezing, having a bowel movement, etc., triggers a fainting spell. I use my chair because I am in pain and because I am scared to faint and hit my head, as I have already done twice. They KNOW this, yet seemed surprised when I reiterated it.

They ran more blood tests yesterday, realized I was severely anemic, and am now being put on iron supplements.

That could explain my issues now, but when my symptoms first started, I was not anemic. That was the first thing they ruled out. I haven't been anemic for years, not since I was around 19. My doctor is now telling me that I couldn't have gone from having good iron levels, to having practically nothing during a six month check up, so she's run more tests and has ruled out pretty much everything out there.

I was desperate and asked if she believes it is POTS (as another doctor told me it could be) or if I have Ehlers Danlos syndrome since I have so much joint pain (was told that only happens in children) or if I just suffer from arthritis (was told no). Now she's worried that I'm losing blood somehow or that my body just won't accept iron. Says that I've probably been suffering from anemia for years now, which is why I am so sick. That is a lie. I know it to be. She ran the tests not even a year ago and my levels were fine, so what is this?

Do you guys have an idea on what it might be? I'm so sick and tired of being sick.

Is it my anemia? Is it my orthostatic hypotension that caused my anemia? Did I actually have anemia before my orthostatic hypotension was diagnosed, yet somehow my levels weren't showing up as anemic?

If you all have advice, I'd really appreciate it!