You have to check the reason why your baby throw up. It might not be your milk! It could be the baby drank too fast or the baby drank too much or even the baby was not feeling well.
Perhaps start with breast feeding once a day in between meals and see if your baby is getting used to be back to breast milk. Let's see what happens, then we can decide the next step.
You should call for help with La Leche League group, they are very experienced. http://www.lalecheleague.org/HongKong.html
Leader Information
La Leche League Leaders are experienced mothers who are accredited by La Leche League International to help mothers and mothers-to-be with all aspects of breastfeeding. For breastfeeding support contact: