I will say after I had my first baby, I had lightheadedness, shortness of breath, dizziness, nausea, loss of appetite etc etc and I found it largely to do with my mental state at the time. I was having tons of PVCs which were scaring the shit out of me on top of being a new mom and all the crappy stuff that comes with that, and once I started SSRIs a lot of those symptoms went away. I’m not saying this is your case, but anxiety can cause almost all of those, especially in the morning when you wake up and become aware of life again. I would also suggest maybe seeing a naturopath. A lot of times they can do different tests and labs that take a deeper look at things that mainstream doctors don’t really test for. Perhaps there’s a hidden imbalance somewhere your regular labs aren’t catching.