Your T should definitely not make you feel like it's your fault. Please erase that from your head. It will not help you in any way.
I get periods of severe depression also. I've found that I just have to ride it out. I do my best, snuggle in bed, watch youtubes that make me laugh, pet my cat and generally try to sleep a lot.
There is only one certainty in life and that is things always change, including ptsd symptoms.
This will pass, just try to ride it out and if you need to express yourself, this is a safe place.
Hugs to you and comfort to your soul.