Wkcookie, I'm so sorry you're struggling hard and blaming yourself. Grief is such a cruel feeling and so hard to deal with, and you don't deserve to have guilt on top of that.
I don't doubt for a moment that you were doing the very best you could for your beloved dog at the time. Doggie illnesses and physical problems as they decline are sooo hard on us emotionally. You had other very stressful things going on also. You are one human being who was being very stretched by everything in your life. And your dear dog was very ill. I hope you will let yourself off the hook and try not to blame yourself for the illnesses that took her life. I so relate to your saying you let go of the only good thing in your life. I have felt that way over and over about losing my precious girl. But I also want my heart to be an open and a hopeful heart and to believe that there is more good to come, even if today I don't know what package that goodness will arrive in. I'm so sorry your life has been so painful and for how disappointed and hurt you feel after losing your sweet one. Take care of you. I know it's hard and grief is exhausting. Thinking of you and sending hugs!
-Missing Marissa deeply