What Could Be Causing Cough, Vomiting, Blood In Stool And Constipation In A Toddler?

Hello my 1 year old baby turning 2 this July 22 I ve notice that every after dringking nido jr milk he cough and cough and led him to vomit.. before when he s months old he has some blood on his stool and he s constipated he s milk is nan but when we tried him to lactose free milk he s become ok.. but now he s poop is ok no stool no skin rash my only concern is he always vomit and cough after feeding.. by the way we bring him in pedia already the pedia prescribe antibiotics cough and cild medicines but still nothing change. Pls help me.