Frustrated with doctors (xpost from r/POTS)

I'm pretty sure I have POTS. I've had heart issues for some time, I was initially diagnosed with arrhythmia and put on digoxin back in 2011. (I was on it for about 3 years and it was an awful experience and I ended up in the ER). I switched cardiologists and got partnered up with an EP specialist as well and after my 3rd holter monitor and 1st month long event monitor, I was told I had Inappropriate Sinus Tachycardia. I was told that the treatment plans included ablation and potentially a pacemaker. Never followed through with that (partially thanks to a lapse in insurance). Heart issues continued.

I started to think IST was a bad diagnosis because my resting heart rate was usually 70-85 bpm, and the event monitor showed my heart go from as low as 50 bpm at times to as high as 160 bpm that correlated with some lightheadedness I recorded in my journal. I did not have the resting heart rate of over 100 bpm like in IST.

After a bad episode that has been ruled as either a seizure or syncope (which I was hospitalized for, even though no prior seizure episodes, and after an MRI and CT no proof it was a seizure) I had a doctor in the ER ask me if I knew what POTS was because he suspected it. It was the first time I had heard of it. Fast forward to the last few months plus over a dozen ER trips and multiple other doctors bringing up POTS I find myself still with no diagnosis. I wore a 48 hour holter which had my heart all over the place, from low 40s to high 160s. I've personally monitored my heart rate with a handheld SpO2 monitor and have seen it jump from the 60s to 130s just from standing up. I did miserably on a treadmill stress test (I couldn't even handle 5 minutes) and today I almost blacked out about 20 minutes into my Tilt Table Test (only to have the hospital staff tell me it was syncope). And yes, my heart rate jumped up during the test fairly significantly, except when I was actively blacking out.

I had to practically beg my doc to schedule the TTT and now I'm worried that I'll be misdiagnosed again. He doesn't think it's POTS (and he ruled out IST again which I'm fine with) and he's been very dismissive. I already have fibromyalgia which I know is a form of autonomic disfunction so I feel like having POTS would make sense. I get lightheaded on my feet, always tired, I have a ton of GI symptoms (GERD, possible GP), cold extremities, headaches, vision issues, neuropathy, etc etc etc. My follow up is next week and I'm bracing myself for a wastebasket bullshit dx. I feel at this point it might be best to see a doc that specializes in dysautonomia but I'm worried that I wouldn't get referred by my local doctors :(

If anyone has any input or has had success seeing a specialist, please let me know.