Weight loss help pronto!!?

I need to lose weight. I'm not obese at all. I am about 5'7' - 5'8' and I weight about 175. I have tried everything I can but nothing works. I do not drink any beverage that has sugar in it. Including orange juice and alcohol. This is because I am a type 1 diabetic. I must lose 25 pounds if I am to be at a healthy weight in order to better manage my diabetes. It might not seem like it to others, but my doctor even says that I need to lose the weight. I limit my portion sizes and eat whole wheat breads(as I have always done since birth!!). Last month I worked out 5 days a week for an hour on my tread climber. But, I didn't lose any weight. And I mean nothing!!!!!!! If you think my workouts aren't at a high enough intensity I either walk 2.5 miles, run 1.5 miles, or I use the tread climber part and walk at 2.0-2.5 mph until I burn 500 calories (roughly 45-60 minutes). By no means is my body used to this seeing as how I alternate my goals and workout daily in order to encourage my body to just "Let GO" of the fat.