My partner uses an old plastic drinks bottle to put his sharps in whilst out or at work. Perhaps you could do the same.
When I was a care home manager I let my staff use my office if required and I would of never said that they'd have to use the loo!
My Hba1c levels were very high when I was first diagnosed. I saw the diabetic nurse the day after and she started me on sukkarto (slow release metformin) straight away and I cut right down on my carbs and on my last blood test week before last my levels have dropped considerably.
I'd try...
I was in metformin when I was first diagnosed and really couldn't tolerate it and had a constant bad stomach. I spoke to my diabetic nurse and she changed me to a slow release metformin called sukkarto, which I'm fine on.
You will probably find you have a low b12 due to the diabetes and not the metformin.
I was diagnosed with an extremely low b12 the same time as the diabetes and the GP said it was down to the diabetes
Try using an anaesthetic cream on the injection site. I'm terribly needle phobic and this allays one of my fears.
I buy mine over the counter at boots and cover the cream with a tegaderm dressing