1) I think the answer to your (TEMPORARY!!!!) struggles is anesthesia. It takes AT LEAST one week to recover from its after-effects, and longer for most!
2) It is also really, really common to have these "why did I do this????" thoughts!! I was prepared for this when I had an elective surgery several years ago. The surgeon gave us a packet that went into this issue at length and it is all temporary, I 100% promise you!!!! You are EXHAUSTED right now!! Your body is recuperating!!
As you probably have in read many, many posts in here on BP, the chorus line is "WHYYYYYYY didn't I do this earlier???" You have given yourself a tremendous gift - a second chance at health and...vibrancy!! This regret, remorse, what have I done feeling is going to pass!!
3) The 8.5# weight gain is also TEMPORARY. FAKE. WILL BE GONE VERY SOON. Remember that needle stuck on the back of your hand attached to the hat stand-looking thing with bags on it that you had to drag everywhere during your hospital stay (which I am going to gently remind you was only a MERE few days ago, my friend!! Be kind to yourself!!)? Those bags pumped your body with a lot - A LOT - of fluid. That 'weight' is going to be gone, plus more, VERY VERY SOON!!!
So...I am hoping you find that place of optimism again very soon and please know that you have all of our support, encouragement & sincere wishes for your success and a brand new beginning!! Even if you don't feel it every second of the day during this journey - You've GOT this!!! You really do. xoxo