Loose stools and vomiting. About this).

My son who is 4 years old has been vomiting once a day ( volume is quite large) since 3 days. Also passing loose stools 1-2 times a day( after we returned from a trip) I consulted a local pediatrician and he recommended Rntac syrup, Ondem Nad Enterogermina along with drotin for stomachache yesterday Eve. But after taking medicine his condition has worsened and he has been passing loose stools more frequently and consistency is also very thin. Should I contact the doctor again or this could be due to something else. Generally he vomits after taking milk or curd and undigested (curdled) milk comes out when he vomits. Should I stop giving him milk altogether or can I give by adding water. He has been able to eat and retain apple and khichdi today. Also I am giving him ORS dissolved in water. He has also lost 1 kg weight (already told the local pead about this).