Hi,
Thanks for writing your query.
It will be helpful if you mention the age of your son.
After reading your post, it seems that your son is having
lactose intolerance.
But since the abdominal symptoms are associated with
vomiting, chances of infection should not be ruled out.
I would suggest that you should get his stool examined for any infection.
In the meantime, you should give him pre/
probiotic after getting him clinically examined. Also antiemetic will help in controlling episodes of vomiting.
If reports suggest infection, then an antibiotic/antiamoebic can be added.
You should maintain his hydration.
I hope this is helpful to you.
Thanks.