I am lactose intolerance (but depends on how much i consume). would lactase pills be effective after symptoms show?

Lactose intolerance: Lactase (http://www.Drugs.Com/cdi/lactase.Html) is a great option for those who are lactose intolerant which as you've noted, depends upon what & how much you eat. Lactase won't work for everyone but it's worth a try.

Using the enzyme: The enzyme must be consumed along with whatever lactose containing foods you eat for them to be effective. Taking a few tablets before a meal is the common use. Once you have developed symptoms they cannot reach/effect the process.