My teenage son did not like the way he felt when he was on dex and pred, he was emotional, also felt very angry and depressed. I am sorry to hear you are feeling so down, are you sure you are on the right dose of dex? I would guess, it could also have something to do with being at the age you are, it is a difficult one but maybe you should have a word with your endo to check your levels? Have you tried the other steroids and did you feel any different? Dex does this to some people and hopefully they will answer your post.  I hope you feel better soon.