Also, has anyone with alexithymia done mindfulness?

Alexithymia: difficulty or inability identifying and/or verbalising emotions, feelings. Often they'll be unrecognised bodily sensations, where you notice the sensation but it doesn't get recognised as emotion.

Alexithymia can be inborn or acquired from trauma, or both.

So depending on the severity of alexithymia, some of your emotions could be just bodily sensations where you cannot do any top-down processing and control of emotion.

(ArmorPlate if you are still reading, I don't know if you had that.)