Are her nappies still wet hun, or are they dry when you go to change her?

I'm not too sure whether it's a gastro thing or something else....are the spews projectiles or just upchucks?

If her nappies are dry, I would take her to a gp or ED as (as I'm sure you know) dry nappies means dehydtration...if the are becoming less and less wet, but still wet I'd head to the gp and just get her checked over.

Does she have a temp at all?

I know I probably am not helping at all, but my overall suggestion is, if you are worried (and clearly you are and I don't blame you), go see a Dr...let them think you're a crazy woman if they want, she is YOUR child, and you are worried about her....