remember to do 记得要去做某事,
(to do不定式不是所有时候都表示将来中,但做remember的复合宾语的时候,的确是表示将来)
remember doing 记得做过某事
所以你这句话应该说:i don't remember whether turning off the light or not.
或者也可以用动名词的完成时,i don't remember whether having turned off the light or not.