Cantaloupe is a great juice, however take it by itself. That's one you're not supposed to mix according to what I have read.
Sounds like you are doing great. Weight gain is normal for the first couple of days, as there will be some light digestion. After that you begin to lose again.
As I mentioned before I was, in the beginning, also unable to drink only 3 - 6 cups. At the end I was at 6 cups.