I've been addicted to both, but not both at the same time. That must be hell trying to get off of. My first question would be did you quit the Xanax cold turkey? That is a medically dangerous situation where you could actually have seizures, develop psychosis, and your anxiety will go through the roof. You need to a proper taper under the care of a doctor. It can be any doctor, it doesn't have to be be a psychiatrist. To help you understand what the Xanax, which is a short-acting benzodiazepine, does to your mind and body, you should be able to consult The Ashton Manual. It is the gold standard for proper withdrawal after long-term use of these medications. She goes into how to properly taper from these medications. I hope you have an understanding doctor and you can show this to them. Most of them are unaware of how carefully someone needs to cut back. I think her schedules are a little too drawn out, but again, your best bet is to work with a doctor. It's even better than detox and rehab. They take you off on the schedule your insurance pays for, not by what's best for you. This is a lot of info to take in, but it might help you to focus on something. There's also an online support group called benzo buddies that support each other through tapering.
I don't know what your exact situation is, but I was addicted to meth full-on hard when I was young for about 8 years, so that part I can relate. It's not a danger to yourself to just stop that, in fact speed is difficult to ween yourself from. It always put my brain into more mode. But I did feel depressed and like I couldn't face life for a good year after I stopped. There is some weak evidence that Wellbutrin can help with meth withdrawals, but there's a high risk for seizures. Since you're withdrawing from Xanax, it's probably not worth it. I would say you could go to NA/AA for support, but it's finally coming out into the light that this approach does not work for everyone. Plus if you have to ween yourself from the Xanax, you can't count that time as "clean" and you may even be harassed about it if you tell people.
Is your career in complete danger of falling apart? Is there any way to hold on to it, especially if you have insurance? I really would hate to advocate for you to talk to them about your addiction, but a lot of places now actually have policies in place that they will help any worker who reveals they have a substance abuse problem and then give them a second chance. Unless you really hate what you do, it may be worth a try. You will need to go to some kind of rehab though; I would suggest outpatient with an outside doctor managing the Xanax withdrawal.
Finally, I'm sending you TONS of hugs.
Both of those withdrawals are nightmares; I can't imagine doing both at once. If you're prescribed the Xanax by a doctor you may want to stabilize yourself from the meth withdrawal before attempting the Xanax withdrawal. You'll be likely to sleep through a lot of it.
Disclaimer: These are suggestions, and we are a pro-choice group. That means all options remain open and no one should be preaching to you to think positive and soldier through whatever. Also, if you're abusing drugs, that generally means something else is wrong, and that may need to be dealt with in therapy. That's a maybe, but it's true for most people.
I hope this wasn't too much; I can just really feel for you and I have a place in my heart for anyone going through withdrawal. You can always PM me for extra support whenever you need it. I did have a lot of good years when I was younger and quit drugs. I ended up having bipolar, but even that was manageable for awhile. Good luck and you're accepted here regardless of what you choose.