Have you had antibody
testing, c-peptide and insulin levels
testing? This would be interesting to know, as possibly you are type 1 not type 2.
For insulin, bottom line is, you need to normalize blood sugars. When this cannot be done with oral meds and diet (seriously look into strict low carb eating if you are not already) and exercise (exercise decreases insulin resistance), and keeping weight on target, then it is time to add insulin.