You do not suck. You just need to learn from failure, it is a good thing that you fail at something. Our flaws are a wonderful thing. We do not achieve anything without flaws.
I read your messages. I feel that you are trying so hard and too often. Perhaps you can take a break and just focus on something else. For a month or two do not think of your health and fasting, obsession is not good in this case.
Rest and do some other creative stuff. Eat raw and hand made foods, nothing from a supermarket. You can have small goals like that. Even if you eat one raw meal a day that would be good.
I am sorry but prayers cannot heal your thyroid. It is good to feel good about prayers, but be realistic.