Tianeptine works through several mechanisms, you have to look at the mechanisms and then at what your symptoms are, and how they might relate.
Right, so you have chronic fatigue and SCHIZOPHRENIA (auditory hallucinations are a sure sign of this) ... are you SURE it's fatigue, and not something called Anhedonia? Anhedonic depression is often a state induced either by negative symptoms, or from malicious auditory hallucinations, in people with Schizophrenia. It's a feeling of there not being any point to anything, and nothing can entice you to do stuff, since it doesn't mean anything.
Well, if it IS Anhedonia, then Tianeptine does indeed treat it! Tianeptine is a stimulating antidepressant, which works by the following mechanisms:
Dopamine
Norepinephrine
Glutamate
Opioid
It alters the activity between the glutamatergic NMDA and AMPA -receptors - somewhat similar to Lamotrigine (lamictal), which you may have heard of. It also weakly agonises, increases the activity, of the Mu and Delta opioid -receptors, this is most likely the source of the addictive properties of Tianeptine, when taken at very high doses. (therapeutic doses are however far below those, even DOUBLE the therapeutic dose should be ok, actually)
Finally, it also lowers plasma-levels of Serotonin, possibly working as a SRE - Serotonin Reuptake Enhancer - however, even though this effect was believed in the past to be the main mechanism of action of Tianeptine, more recent data has shown that this effect is almost entirely occuring in the PERIPHERAL nervous system - outside of the brain, and not inside of it. As such, it affects things which serotonin controls OUTSIDE of the brain, but not inside it. (this is why tianeptine actually affects some forms of Asthma, improving symptoms)
Some times, combination-therapy of substances which individually affect these multiple networks in the brain, which Tianeptine affects all on its own, can lead to relief from anhedonia.
Please also note that I'm not entirely certain how or where Tianeptine increases dopaminergic and norepinephrinergic activity, so look closer into the mechanisms on your own, and make your own conclusions.
For what it's worth, I have also experienced the feelings you experienced, while suffering from Occupational Burnout (which causes something similar to chronic fatigue, just not as chronic) taking Tianeptine Sodium - this may however not be a TRUE feeling of relief, since Tianeptine Sulphate did not cause these euphoric sensations, but did have some antidepressant effects still.
You may instead have been somewhat high, really...
But, I digress, look closer into Tianeptine and have a look at how it works, and figure out if this has anything to do with your diagnosis and perticular brain-alterations. It should be noted that it's generally considered that the actions on GLUTAMATE is the primary action of Tianeptine, and the network it alters the most, even though it does alter several other networks, to some degree.
References:
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Tianeptine: a review of its use in depressive disorders.
https://www.ncbi.nlm...pubmed/11463130
Tianeptine: An Antidepressant with Memory-Protective Properties
https://www.ncbi.nlm...les/PMC2701287/
Neurobiological and clinical effects of the antidepressant tianeptine.
https://www.ncbi.nlm...pubmed/18072812