Take 2

[Delicious]

I agree with BynineB, it's flat because you don't have any shades and your light source is all over the place. Assuming it's coming from the top left hand-side because of the highlights on the eyes, you could approach it like this:



It's quite a messy edit, and there are a few things that I didn't really do or fix, but hopefully it gives you an idea.

Keep it up, it's looking great!