i understand your son burps a lot .
1. burps are common in children.
2. keep watch on his food intake - make a dairy of what is food he takes ( everything ) without missing anything. then, you can pick the foods which make him to burp a lot . you should avoid those foods or minimise the amount .
3. he should take plenty of water and go to toilet regularly , so that he is not constipated.
4. i am not sure whether he takes bottles - for milk etc ---as you know some children do take bottles even as a toddeler. in case if your son takes , stop it and switch to mugs/cups.
5.regular tummy massage after the food also helps.
6. if you notice any other symptoms like loose stool, loss weight , indigestion etc, please see the gastro dr.
i hope this information is useful.
thank you ,