4yrs old not intrested in eating.

My son 4yrs old(26th feb 2018) ..weight is 16.5.the main problem with him.was eating..from childhood he is not showing intrest in eating..he doesnt even feel hungry or not crave for any food even though left for hours..evrytime i take a to a dctr they says he is good with height and weight so dnt wry but i feel some problem is there as forcing and keeping food is not solution every time but i want him to show intrest in eating..they give medine cypon and some syrup for 1mnth ..that 1 mnth he will be ok in eating..but not with intrest..plz help me..dnt reply with saying consult online or still details needed..if anyone who can treat or can help me onlyreply with solution..some say that he may have some stomach disoreder so he is not feeling hungry..how to increase his apetetite..