What could cause drastic fluctuations in the blood sugar levels in a 20-year-old diabetic?

Hello doctor,

I am a 20-year-old female. I have been suffering from diabetes for two years (my diabetes is not confirmed yet). Four months ago my blood test showed Insulin 71 µU/mL, FBS 101 mg/dL. I took metformin for three months and my insulin came back to normal but my FBS showed 113 mg/dL. My doctor prescribed me Metformin with Inositol for three months. After taking these for just 20 days I started feeling nausea, and difficulty sleeping. Extreme headaches, heavy eyes, and I almost became unconscious. Noticing these symptoms my doctor said to monitor my blood sugar by glucometer at home. After monitoring I got extremely low blood sugar level results. A week ago the FBS in the glucometer was 45. I drink sugary drinks as it was suggested on the internet and my sugar was so unstable in the glucometer. Yesterday my sugar became 89 mg/dL in the glucometer. I took a lab test and it showed 113 mg/dL again. I do not understand if my blood sugar is unstable or if it is the fault of a laboratory test or my glucometer. Please suggest to me what to do.