My doctor told me this was hypoproteinemea when the body is in severe protein deficit. This happens with starved children in 3rd world too.
Sure enough when I gradually added protein the symptoms you described (and much more severe) went away. I thought it was lack of bacteria in the gut, but evidently not, as probiotics and yoghurt only marginally improved the situation.
Without adequate protein stores our body cannot process/digest/absorb food and just rejects it.
Try to gently add plant proteins: spirulina and chlorella are good to start with, yoghurt is also good, and try to move to full proteins with all aminos and your body will regulate.