Hi. I am sorry to hear that you are having so many problems. I am also sorry to hear that the docs are saying that you have anxiety and that is causing your symptoms. Neurologists said to me that it was all psychological. I know different now. To me, it sounds like autonomic dysfunction and could well be POTS. A tilt-table test is the only way to check this out. There could also be some mast cell issues as some of your symptoms suggest that this is the case. The breathlessness, tachycardia and gastroparesis are all linked to autonomic dysfunction. You don't necessarily pass out with POTS, only if you get Neurocardigenic syncope.
My symptoms started after Glandular Fever and I was eventually diagnosed with ME/CFS. In more recent years I have been diagnosed with Ehlers-Danlos (The underlying disorder), POTS, neuropathy etc and may well have mast cell issues because of allergies and intolerances. They are all linked. I am often deficient in vitamin D. I get very breathless and cannot tolerate exercise etc very well. I have tried beta-blockers and Ivabradine (it upset my IBS) and I am now on Nebivolol to see if it helps with the flushing, fast heartbeat etc.
So a tilt-table test would maybe help you and looking into other possibles as I have listed. Good luck, as I know it takes time to sort out. I also think some relaxation therapy like meditation can help a lot and not pushing too hard when trying to do tasks. I also suggest a warm, not hot, shower and then cooling the water at the end. Maybe the cannabis is best left unless you are taking CBD.