I'm just heartbroken to hear about your problems. I'm so sorry that Benadryl cream doesn't work for you, because it was so helpful to me, and so soothing. Since your eczema covers so much of your body, I would definatly look to whether you are allergic to something you are using as a detergent or soap. Try using hypoallergenic products such as Cetaphil gentle cleanser for sensitive skin or Aveeno non-fragrance body wash. I use fragrance free Tide and Downy for the laundry, but there are other fragrance-free detergents. Non-fragrance shampoos are also helpful. I like California Baby, which I order online, and DHS, which I have bought at the drug store. Shea butter is a wonderful moisturizer because it's natural. Oatmeal bath soaks also help to relieve dry, itchy skin and eczema. Aveeno makes a colloidal oatmeal powder for the bath that is very soothing. The oatmeal works as a silky skin protectant, too.
It's also very important to eat a very healthy diet. Are you under a lot of stress right now? Stress is an eczema magnet because it increases the level of cortisol in our bodies, which increases the free radicals. The free radicals inflame our nerve endings, which causes eczema. I wouldn't think that juicingWatermelon is what is key, but instead, eating the beta carotene found in the watermelon. As Watermelon goes out of season, however, there are other foods high in beta carotene, such as sweet potatoes, yams, and pumpkin, but there are others. You may want to Google "foods high in antioxidents" to see if there are any you like in particular. One thing about eczema, is that we have a laboratory on our skin that shows us just how bad cortisol and free radicals are for our bodies. No one has to tell us that free radicals are harmful to us internally, because we can see their effects on our skin.
I don't like using prescription hydoochortisone cremes, but since you are so miserable, it might be the best place to start at first. If you can get your symptoms under control with hycrocortisone cremes, then you can move to the more natural solutions.
I'm wishing you the very best, and please, please, let us know how you are getting along.