Thanks everyone for your replies.

DD seems to be much better now the last 12hrs she's not vomited after her feeds and seems to be more herself. She's sleeping a bit better too but that's also cos' I'm learning her tired cue's better and actually putting her down before she gets overtired!!
So everything seems back on track. Just didn't want her to keep vomiting little bits all the time as then she'll be hungry!
Miss C - thanks for your reply, very helpful. Yes I think DD has been taking milk more effectively and she feeds for less time now too and seems full so I think that's also what it could be. I was so used to her feeds taking up to 1hr at a time before whereas now she seems to feed in 20-30mins and be full. It's great!!
And yep, plenty of wet and dirty nappies so that puts my mind at ease about what you said re: they reach a plateau. Plus I think my DD just isn't a huge girl... she's petite hehe