I prefer chocolate milk drink when i was a kid. now that i'm 21, i bought vanilla milk drink and i experienced lbm, is it possible to develop intoleranc?

Yes: Intolerance to a food or some component of the food can be present at or near birth, develop later or be transient after some infection of the intestines. Intolerance to the sugar in most milk, lactose acts this way. Avoiding lactose or taking a supplemental enzyme can stop symptoms. You may also have a specific problem with another component of the vanilla milk.