A meltdown is an instance of furious overload reaction. It is overwhelming and exhausting and constantly intense until you find some way to calm down.
What you are experiencing sounds more like progressing into depression and possibly a shutdown mode. Shutdowns can definitely be longer term than meltdowns. One can live in a state of shutdown, just kind of.
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"Listen deeper to the music before you put it in a box" - Tyler the Creator - Sandwitches