Insulin resistant but healthy BMI of 20??

Hi! I was diagnosed with insulin resistance a while back and got on medication for it and lost a bunch of weight. I had decent lifestyle habits and ate relatively healthy wi the a weakness for sweets and was a dancer my whole life before gaining weight so have a lot of muscle and relatively active lifestyle. When I started I was slightly overweight (150 pounds 5’5”) and lost A LOT of weight because of metformin/ semaglutide. I hat to stop because it got to a point where I became underweight, my insulin and glucose levels where back to normal and decided I had to gain back some weight to be at a healthy weight.

Fast forward to today, i’m happier than ever with my body, I weigh 120 pounds and have a BMI of 20, I stopped taking any medicine for insulin resistance years ago and rarely feel hungry besides my usual sweet cravings so i’ll just have a piece of chocolate a day or whatever, but lately I started to notice a LOT of fatigue, mood swings and cystic acne so i run some tests solicited by my endocrinologist and to my surprise insulin is at 18 and glucose at 103 which puts me on 4.6 in the HOMA score.

My doctor wants to put me on metformin, the thing is i don’t want to loose weight anymore, i already have trouble eating as it is because of ADHD medication and have to make an active effort to manage nutrition and some days the idea of eating makes me sick. Metformin in my experience significantly reduces appetite. My dermatologist thinks that based on the same lab results i might have PCOS so i’m getting an ultrasound next week, but this seems odd since my periods are regular…

Anyway, my question is, is anyone on here in a healthy weight and is it normal to have insulin resistance while being on the lower side of a healthy weight? And secondly, can I fix this with a certain diet or lifestyle change?

Some info: I eat relatively healthy, maybe less than I should (around 1000 cals) but in general whole foods etc. I have a weakness for candy so i’ll have maybe one sweet treat a day and eat out maybe twice a week (half of the time fast food or fried). I drink lots of water and do yoga or Pilates three times a week on average (sometimes more sometimes less)… I walk at least an hour daily. I’m bad at managing stress and lately i’ve been very stressed because of masters applications and work, could that be a factor? I sleep 8-10 hours daily… Oh and I have hashimotos disease but no hypothyroidism yet don’t know if that’s a factor… Rarely drink, sometimes smoke… In general I think i’m healthy which is why u don’t understand why I still have this. I’m willing to follow a specific diet plan I just really don’t want to take medication again.