Actually most adults in the world are unable to digest dairy. African, Asian, Indian, Native American... As children it is not usually a problem, but as they enter adulthood, the body starts to reject it.
However, people of European descent typically do not have a problem, as their ancestors possess a genetic mutation that prevents the body from rejecting it. Since many people in the US are descended from Europeans, it is a common drink here for adults as well.
This is well known by most doctors. However, to be able to drink & process milk & other dairy products well into adulthood before having problems is not as common, and probably is not something most doctors would think of, especially in this country.
For a doctor who trained in India, it is likely more prevalent to think of allergies & intolerance to milk for adults, which is probably why he was the first (only?) person to suggest it.
Lactaid (pill) is simply the hormone that many adutls stop producting; when taken while eating dairy, it allows the body to digest the lactose present. The Lactaid milk is produced by taking out the lactose that causes problems, allowing people to drink it without problem.
But, if you were able to digest dairy until recently, & assuming you are older than 20, it's hard to say if Lactaid pills will be effective, or if your intolerance is perhaps due to a different reason than no longer producing the hormone required to digest dairy.
A friend of mine has a son who is severely sensitive to dairy, to the point where he cannot eat things made with butter, or even be touched by someone who handled dairy products.
My personal instinct would be to do this sooner than later, as avoiding dairy for a lengthy period of time may make you more sensitive than you might otherwise be (thinking of someone who goes vegetarian for years & then decides to have a steak) but do check with a doctor you respect & are working with, as the opposite may happen, & more exposure could cause a continuation in your sensitivities.
Best of luck! T.