No diabetes, normal fasting insulin levels, gaining weight fast, no thyroid issues, but low fasting glucagon levels (25pg/ml), no energy, healthy diet?

Exercise?: The only thing you didn't mention is exercise. That can be a vital component of good health. Please check w/your doc about your fitness to do some exercise. Simple walking can be helpful. You said no diabetes but i see metformin in your med list. Looks like your doc want to keep your blood sugar balanced. Is your diet balanced? Peace and good health.

Sleep disorder: Check for sleep disorders (insomnia, sleep fragmentation, sleep apnea, restless leg syndrome). You do not have diabetes.