I understand you too well.
I never asked for a proper diagnose, but i always catalogue about these feelings as depression.
It is defintely triggered by something that maybe is too down under in our psyches for us to recognize them.
The worthlessness feeling is typical.

How about going back to therapy? Not only change medication, but reporting these feeling to a therapist and try to sort that out'

It's not easy, you need luck too, but it's very important.

My heart goes to you.