speech problem

Hi everyone.. im glad had this community that can share and ask for an opinion while growing up our childrens.. ok i have 1 question that need ur opinion here.. my eldest child 4th years old.. recently he had problem when try to speak up.. his voice seems got stuck when he tried to speak. he had to take a deep breath everytime when he want to speak up.. i am so worried seeing that.. others he is normal. just recently i notice this prob occurred.. what shud i do and who/where shud i refer to.. tq.