You should always involve your Doc. in your decisions regarding medication, Metformin could be doing it's job and bringing your BGs under control, it works a lot better in those who still have some insulin production and even helps the pancreas to recover from it's years of hard work.
If you tolerate it well and your Bgs remain good, I would discuss it with the Doc. To stop it completely would, IMHO, not be a good idea, there are other protective effects on the heart, liver, etc. from Metformin that you would lose if it was stopped completely.
I like my Metformin, it has allowed me a reasonable choice of diet and the odd treat without any spiking problems, so why change?
H