Don't be fobbed off, ask for an alternative drug as there is one I'm not sure what it is called but I know there is one. If you are not happy with the GP you could also contact your nearest hospital and ask them if they have a special clinic I understand that most do. Then take it from there see if you can be dealt with in the hospital rather than GP as you are unhappy with how they are dealing with the situation. If that is not an option then think about changing your GP practice.
I had problems to start with but find that if i take metformin with or after meals then its not too bad and i try to follow LCHF. I feel loads better for not eating bread, spuds, rice and pasta especially.