First you really do need to be under a physicians care. And I applaud you for taking your health in control.
There are two diets that are healthy and effective. One is the modified Atkins diet and the other is the South Beach Diet. BOth are effective.
You have to get serious about counting carbs. Try to only take in 40-50 carbs a day. This is net carbs which means that you take the total carbs on the label and subtract the fiber carbs, that is your net carb value. So there are good carbs in the fiber carbs.
Walk 10 minutes at a time for about 4-5 times a day. Any other exercise will need to be approved by your doctor.
I promise you this will make a difference.
Like the total carbs will be 20 but the fiber carbs will be 12 so that would be a net carb of 8.
Don't try to make sure the sugar and fiber carbs equal the total carbs because sometimes they just don't but do subtract the fiber carbs from the total and you will get the net carbs.