It doesn't sound like you are eating enough calories. If you eat too little your metabolism will stall to a crawl and weight will become harder and harder to come off. The worst part of it is that your body will start to burn muscle instead of fat.
Your diet is also pretty high in carbs. You need to incorporate fruits and veggies and more protein into your diet as your diet isn't too balanced.
Even if it is a medical condition such as hypothyroidism you should change your diet to include whole grains and the other items already listed. Eliminating refined and processed foods will also help your dieting. I would strongly suggest reading the doctor phil weight loss challenge as his diet is very balanced and he focuses on changing your liefstyle and not "dieting". Another good book if you don't like dr. phil is the new glucose revolution which talks about a low-glycemic diet which is a very healthy and satifying way to eat (it is the same type of diet dr p is advocating.
You may want to go to the doctors to see if it is your thyroid, the tests to ask for would TSH, Free T3 and Free T4 as well as the thyroid antobodies test. You should visit the thyroid board to see if you recognise any of the other symptoms. Good Luck to you.