Compression of the Left Renal Vein Nutcracker Syndrome) can cause the same problems such as Left Side Chest Pain, Fatigue, Diarrhea, Nausea, and many other problems. Median Arcuate Ligament Syndrome (MALS) can also cause some of these problems as well. Just a couple of ideas as I know most doctors have never heard of these conditions so they are rarely diagnosed.
Hyperthyroidism comes to mind. The most common cause of hyperthyroidism is an autoimmune disease called Graves disease.