A side effect of steroids
is their impact on insulin. Steroids increase the insulin resistance
in the person making the insulin less effective. If you don’t have diabetes
and your pancreas
is able to make additional insulin, your blood glucose will stay within a normal range. If the pancreas can’t make enough insulin to keep your blood glucose within a normal range while you are taking steroids, you develop steroid induced diabetes,as it has happened in you.
Since you can't stop steroids,you have to continue taking insulin.
What to do...
Start taking METFORMIN
to reduce your insulin resistance,but after consulting your doctor.
Restrict sweets and your calorie intake and try to reduce your weight.
Do exercises whatever is possible for you.
I hope it helps