Hello Cherrub55, and a warm welcome to you.
I understand that ' treatment-resistant depression' must be very difficult or you, just before I go on there was a thread 'Long term treatment resistant depression & Anxiety- what next? ' by radarsan on 23 August 2016 and 9 replies were made and one by Dr. Kim who used to be our medical advisor but has apparently moved on now.
This is where you are treated for depression but your symptoms haven't improved and normal treatments aren't enough so perhaps consulting a psychiatrist who deal with mental health conditions, I'm sorry if this has already happened.
There are other ways of tackling this and these are what you can consider with your doctor, ECT, Transcranial magnetic stimulation.
With antidepressants it took quite awhile to find the right AD, my doctor kept prescribing one after the other until finally the one I'm now taking actually works and been on it for so long I can't remember.
The dose had to be changed where I now take the max dosage, so if for some reason it's not working as it was before, then I'll have to start a new AD.
I don't like changing medication, but you can get to that previous thread by typing it in the search bar above.