Hello,
Weight loss can be quite difficult for many people, and I am afraid that insulin itself promotes weight gain. Unfortunately in your situation it is unavoidable.
Other medications that have been approved for weight loss include Xenical and Meridia--have you tried those?
Be sure that your thyroid function is normal and optimized.
If you truly have tried everything, one last option is to discuss gastric bypass/banding with your doctor. This is a very serious operation and should not be undertaken without going through a thorough screening program within a reputable health system/hospital. It is a drastic step but may prove to be a viable one for you if truly all other options have been exhausted. Please discuss with your doctor.
Take care.