Hba1c 5. 9 metformin. For weight loss?

I have been diagnosed with possibly fibromyalgia by the rheumatologist. I have chronic jaw and neck pain with no definite diagnosis yet. Rheumatologist is not sure about the diagnosis and tried different medications. He put me on nerve medicines and I gained lots of weight with those. Tried 4 different medications for a while and none of them helped for my pain..I gained lots of weight from those pills. So the rheumatologist wanted to put me on low dosage of metformin for weight loss now. My recent blood work for hba1c was in December last year and it was 5.9. My physician didn't prescribe any medicine after the blood work and told me to check this value later. I took medicines after this blood work and gained weight. Can we take metformin for weight loss? Is it advisable to take metformin even when we are not diabetic and ok to take for weight loss?