Dog with parvo. What are some signs of improvement?

I have a husky mixed with German shepherd, he's only 7months old and on Saturday (4 days ago) he started vomiting a clear and foamy liquid, had lethargy, loss of appetite, but no diaehrria. So on Monday (2 days ago) we took him to the vet and they gave him two 250 mg shots of ampicillin (antibiotic) and cerenia to stop the vomiting. I brought him home and have been syringe feeding him A/D veterinary food since then, he still drinks water. Last night he vomited twice but this time it was yellow and gooey, he hadn't vomited alll day thoug. It seems like he has gained a little bit more strength today since I saw him walking earlier in the morning but he still looks depressed and has vomited once today and no still no diaehrria..... I really don't know if he's improving or is he gonna get worst? :( I take care of him 24/7 and he's being fighting the virus for 5 days