I am 16 yrs old and recently have noticed my right eye is going lazy, thought lazy eye is something ur born with is that true,could it be brain tumor?

Rarely at birth: "Lazy eye" is the term for an eye which sees less well in infancy which will commonly turn out or in. This is accompanied by a reflex called suppression which prevents doubling of the vision. You may have had this when younger and now it is showing up again. Check with your mirror to see if the eyes are aligned. If not, see a pediatric ophthalmologist for evaluation.