Okay... where did you get her from?
I brought Poppy home a few days before she would turn 6 weeks old, I was told she would be 8 weeks on the date I could bring her home then later found out she was younger.
I was worried too.. she was so small she could fit in the palm of my hand!
The breeder we got her from was a friend but I didnt want to give her back because I was worried about how the breeder would care for her.
I kept Poppy and took her to the vets ASAP for a check up.
Poppy ate well.. I gave her winalot puppy (before I switched to Wainwrights) and Puppy milk from Morrisons. She LOVED the puppy milk and would drink it all, but she didnt touch her food much until I took the milk off her so I guess it was quite filling for her.
The vet told me I shouldnt be giving her puppy milk because she was already weaned and just to give her water which is what I have done ever since.
Just keep an eye on her.. make sure she is never alone for long because she is so small and keep an eye on her weight.
She will be due her first worming at 6 weeks and you will have to book her in for her first needle between 6-8 weeks old. (Poppy had hers at 8 weeks)
Stay calm.. to be honest Its best that shes with you then a breeder who would give her away so young.
You have everything you need.
Which vet are you using? I use Strachan Tyson and Hamilton.. they have a few branches and I find them fantastic. They really care about the pet and NOT the money.
Also can you PM me the breeder names of her parents and grandparents because the little star thing sounds VERY similar to my Poppy's.. Im sure one was little star something and the other little mischeif something or other...
Oh and yes that was me and my BF in Pets at Home with Poppy yesterday

PM me if you need to talk more.
EDIT: Ignore the little star things I read your posts wrong