Welcome Pinocchio (love the name, btw) - I must say you have a lovely way with words. Can I ask how long you have abused opiates for? I see you mentioned a past hx of heroin abuse and now the oxys? Was the heroin before or after the back injury, and how long ago did that occur? I guess in the long wrong, the timeline is not all that crucial. What I'm getting at is, it seems you have a pretty long history with drug abuse and depression/anxiety...have you tried anything, in lieu of self-medication w/opiates or drs giving you a/ds, meds? Have you ever tried aa/na or another program of recovery? As was mentioned above, just cutting out the opiates c/t is not going to work long-term. I think you need to gain some insight, and tools to help you learn to 'deal w/life on lifes terms' - learning how to live drug free and regain self confidence, motivation and your happiness.
I'm sorry you've had such a rough time....and I was actually going to suggest looking into maintenance therapy (such as suboxone) b/c you have a long history of use. It's unfortunate you had a bad reaction to the medication, but not to fear - there are other ways! I personally have never been able to taper myself, get off and stay off...and it sounds like you have had past failed attempts as well. I think weaning down was a good start...but you'll need to throw something new into to the mix to make it work this time.
I know you mentioned that meds (such as a/ds) haven't worked in the past, but it may be worth talking to a p-doc or addictionologist about giving it another whirl- maybe one of the newer class of drugs? Like you said, you won't know to what extent the depression/anxiety is clincial until you get past the entire w/d and detox period...but I really think you'd benefit from medical intervention to get over the hump, as well as counseling, group sessions or an aa/na type recovery program. It's clear you want this, and you know that you need recovery for your own sanity and happiness...keep posting here...you'll get alot of great advice and hopefully make some good friends in the process. Support is so key! Remember that people here are addicts, or love an addict....we understand the 'nothingness' you speak of, the desire to draw the covers over your eyes and hide from the world...and it is beat-able! It feels good to surround yourself with people who 'get it.'
p.s. have you ever looked into methadone maintenance? I know many see it as scary and 'bad' but there are also people here who will sing it's praises. You should talk to your dr - maybe you'd be a good candidate? My fiance has chronic pain due to severe degenerative disk disease, and as well suffers for anxiety/bi-polar type depression. He's been through all the meds and has tried everything (including subs as well) to get off opiates. He does have bouts of intense pain, however, like you mentioned, he was using more to cover the emotional stuff. He is currently doing well on a low dose methadone regime. Just his experience I thought I'd share. hope that helps!