Hi fastest600
Welcome to NeuroTalk

.
I am in remission from MDD. I know somebody with treatment-resistant MDD. She found that Transcranial Magnetic Stimulation (TMS) helped her. This is a possibility that might be worth investigating.
The Headache forum here (
https://www.neurotalk.org/forum32/) could also help. If you describe your experiences there I am sure that you will get support and suggestions from other members.
All the best.