Thanks for your query.
Relax,this is normal for a child to behave like this.
You have to be patient with him ,feed him when other family members are eating,use two spoon method that is take one spoon yourself and give him second one.
Give him fruit juices,vegetable soup as they act as natural apetizers.
I will not advise you to do any self medication
Cypon(cyproheptidine) is anti allergic and increase in appetite is one of its side effects.
Wishing your child good health.