Hi and welcome to PC, sorry you have been living with dysthymia for so long. I also have dysthymia and when, for different reasons medication that had helped me stay fairly well for many years became ineffective I developed severe depression. I too would encourage you to see a psychiatrist, there is always something to try. Do you have to stay with this therapist if you don't feel right?
I really hope you get the support you need, this is a very good place for understanding and support in the meantime.
The very best of wishes as you find a way forward. This community has really helped me and I hope you find them as helpful as I have.