Reading between the lines, and looking at the rapid weight loss you have achieved over 7 months, this suggests you are on quite an aggressive diet, most probably low carb, and possibly fasting too. The Metformin does not have much effect on lowering bgl being effective for only 1 or 2 mmol/l or so with a following wind. So stopping the Met will probably not make much immediate difference to bgl but you will lose the appetite suppressant quality it gives, so you will probably eat more, and put weight back on. Eating more carbs will increase bgl.
I think there is a timing element to this problem too. Are you breaking fast with breakfast? Now that your weight has dropped, maybe your liver stores are depleted, and your body is not able to self regulate. You may find adding a small snack in the morning will alleviate the lows. (Metformin is advised to be taken with food)
The other thought that springs to mind is the possibility of Reactive Hypoglycemia, which has its own forum thread on this site, and perhaps a quick scan there may be worthwhile.