Hello, In_The_Darkness!
I'm sorry about your mum's employment troubles. You're enmeshed in her emotions and that's both touching and troubling. I say "troubling" because you are already suffering and now bear a double burden. Does Mum know about how you're feeling or understand?
Regarding your difficulty sharing your feelings, I think you need to mark it as a problem in its own right. If you feel comfortable doing so, tell your therapist directly what you've revealed here, that you really are very depressed and that you get sick even trying to talk about it, that you don't want to talk about it. A good therapist will take you seriously and work with you.
Wishing you a lightened load...
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My dog

mastered the "fetch" command. He would communicate he wanted something, and I would fetch it.