The article mentions Indians have milder symptoms of lactose intolerance and hence many people are not aware of it. You can try going to a doctor to confirm if you have LI.

"The mystery then is why so many people believe themselves to be lactose tolerant when they are in fact genetically unable to produce lactase into adulthood. One theory is that non-Europeans experience less severe symptoms of lactose intolerance, and thus may not notice the consequences of failing to digest dairy as much. Another answer comes from how Indians prepare their milk – often fermenting it to use as yogurt or paneer, which breaks down the lactose within."