I'm going to bring the mood down here but nobody seems to have raised, to me, which is, the obvious.
You're being prescribed 20mg Diazepam every day (by your GP I assume), which you say isn't sufficient. And that 20mg every 4 hours is more on the ball.
So instead of going back to your GP and saying 'Hi doc, I'm really suffering on 20mg every day, it's just not sufficient, I really need your help and advice. Can we sort out a withdrawal plan with a higher dose, I really want to get off of this shit and I'd really appreciate your support in helping me' ... you've ignored their previous help and gone to self medicate on Xanax having no idea on earth how much to take 'but it's stronger then Diazepam so I'll take it anyway and see what happens.'
After my mother passed away I suffered from horrific anxiety and was prescribed Diazepam, it nulled all of my worries and for the first time I had head space. It was 'the only thing that worked' so after I exhausted my prescriptions I went against my doctors advice and obtained them illegitimately and started to self medicate. I got in a horrible mess months later when my supply was cut off and had horrific W/D symptoms.
I went back to my GP and just laid it out honestly, 'I've been doing a very stupid thing, it's got out of control and I really need your help.' He completely understood my situation and together we created a gradual withdrawal programme over 8 weeks, with me picking up a prescription every 7 days so the amount dispensed was controlled. He's sure as hell seen worse than my case but at the end of the day it's his job to care for me. He knew that I knew I'd done something stupid and spared me the lecture but under his care we both sorted it out together. Since then I know I can always be open and honest with him and we have a great relationship.
Doctors are paid to care for your physical and mental health, we all go off the rails in life, we're human.
Why don't you do the same? Get the help, advice and support that you need where you can be closely monitored for progress by professionals who are paid to do just that. They all take the Hippocratic oath to declare that they will always act in the best interest of their patient, YOU.
It is in your best interest to get medicated properly and sort your life out.