Welcome to HCM
Yes pre-diabetic can use metformin
to prevent /or delay development of Diabetes,If you are Obese t and sedentary worker start a regular exercise daily from at least waking 30 to 40 min daily at brisk pace. As metformin reduces insulin resistance
and cause a loss of weight so keep a watch on low blood sugar
that is hypoglycemia
.Tired eyes and hunger could be due to low blood sugar level you can check with Glucometer.Please also check your Lipid Profile
Take care of your diet and consult a Dietitian to plan a Good protein, low calorie low fat diet approximately 20 K cal/kg body weight and take good amount of water and take small and frequent diet may be every 3 to 4 hours and if required adjust the dose of metformin in consultation of your treating Physician.
If you take care of diet and exercise you will loose weight as well as your blood sugar will be controlled.
Good luck to you