Diet changes triggered disordered eating?

My entire life, I struggled with my weight but probably in the opposite sense from most: I was chronically underweight. I never had anorexia/bulimia or was intentionally trying to lose weight. I just never felt hungry or craved food so ate little. It was only after having two pregnancies/kids and eating richer, tastier restaurant foods more often over time that I finally felt “healthy” and “strong”. As a 5’4” woman in my late 30s I was finally at 119 lbs or so after a lifetime of being 96-102 lbs. But a couple months ago my bloodwork came back with high total (219) and high ldl (153) cholesterol. The doctor suggested diet and exercise changes, which I eagerly made at first. I generally started eating low oil home cooked foods, largely eliminated dairy, and reduced saturated fat to <10g per day and started taking fiber supplements either Metamucil or Olipop soda once per day. My weight has been plummeting. I’m down to 106. I feel weak, scrawny, and have frequent migraine headaches from the dehydration associated with increased fiber intake. I feel like I am withering away slowly and it’s a vicious cycle with my appetite because once again I never feel hungry anymore and have to force myself to eat. I asked the doctor to please please put me on statins so I can go back to my earlier diet that supported my weight but they hesitate and want to focus more on eating more quantity of the healthier foods but my body just doesn’t want to take it in. Anyone ever fall into a similar boat?