Hi, maybe you are losing weight
because of the metformin (it is a known side effect which is beneficial for many). You may also be losing weight because you are eating less calories.
Do you want to lose weight? If you do, continue what you are doing.
If you don't want to lose weight, you will need to eat more calories. These should be from more healthy fats (full fat dairy, butter, cream, olive oil, avocado etc), or by adding more protein (meats, eggs, nuts, etc).
Hope this hlps.