I’m assuming your child is between 1-2 years old. With these symptoms there is definitely a need to see a doctor to establish the degree of dehydration and to rule out serious causes for the incesssnt vomiting.
If the symptoms have just begun and your child doesn’t have fever nor other symptoms and isn’t listless, you can try slow and low volume rehydration with diluted formula milk, watermelon carrot or coconut juice, or medical grade fluid replacement like hydralyte or pedialyte. If vomiting persists please seek medical attention.