Please help I changed my pups food she's 10 weeks old at first she had diarea then spitting up the liquid I gave her she drinks and I give her nutrients through syringe she urinates I haven't seen her spit up for awhile or poop. She's lost weight how long does it take to get better its 2 days gone on three

A 10 week old pup losing weight is very serious. The runs from changing food can last a few days but it is not usually accompanied by vomiting.
This pup needs to be seen by a vet, I know that is not the answer you are looking for but this sounds more serious than just a dietary change.

Thanks for your answer.

Yes I totally agree with Shaz, your pup needs to see a vet asap. Puppys can go from bad to deadly in a matter of hours. It's best to have this checked out my a vet. It could be parvo.