Hollye, I would deffinitely take Mia to the docs. There's got to be something going on for her to be consistantly having such small amounts and not waking herself up to have more. And dehydration can be a real problem for bubs. Might be nothing, and I know as little about all this as most of us, but that would be ringing little alarm bells in me (not pannick bells though, so don't panick ok ).
Good luck with it.