Whoa there. I didn't say anything about sodium.
The "sodium" part of MSG is not the umami part; that's the glutamate part. Basically, the flavor you know as savory and flavorists know as umami is caused by one of the twenty amino acids that form proteins, specifically glutamic acid in its ionized form. The sodium part is simply used to stabilize ionized glutamic acid, which typically exists in deprotonated form anyway (pKa of 4.1) by providing it with a positive ion with which to associate, and render it into a powder much like table salt.
When you eat MSG, cheese, meat, or similar foods, the glutamate triggers an odd bunch of synapseless taste receptors that actually act as middlemen, secreting ATP of all things to excite the actual nerves. Those signals get processed in the orbitofrontal cortex and you taste savor.
So, if you want to taste actual umami and fix what I believe to be a combination of metabolic weirdness and threshold adjustment weirdness (sciencey time is over now), go eat something with a lot of free amino acids. If you're not a vegetarian, meat, particularly really juicy meat, works well, as would meat-based soups.
So that's my advice, and the reason I'd make a terrible doctor. Take two pork chops and post in a day or two.