I am so sorry. I have been in your shoes. I have to work really hard to loss just a little bit. I have to do about two hours of high intensity exercise about five days a week, along with a 1500 calorie a day diet to loss about a pound.
Have you check with your doctor? Mine checked me for thyroid problems, and any other tests. I have an autoimmune disease and am anemic. My doc says that these things cause me to have a slow metablism. Alot of people us that as an exuse, but for some people it is true.
My advise to you would be to find an exercise you like and do it more. I really like the Turbo Fire DVDs.