((((little mouse))) sure can relate to your post. i have found that sometimes stressful situations-like your back surgery-can lead to a down swing. it's like a boomerang affect. i get through something serious then fall apart later. that may be what's going on with you. i'm glad you see your t soon. talking about it can pinpoint what is causing this mood.
by the way, i had the same surgery and it is a big thing. i was terrified but like you i was becoming paralyzed so there was no option. hope you will let us know if your session helps you sort this out. (it's usually life stuff that triggers my depression i've found.)