At what age we can safely administer bottle without developing nipple confusion.now my breastfed baby is 2 month old.he developed nipple confusion at one month ?

There is no age where you are guaranteed an infant will not develop a feeding preference, breast vs bottle or the opposite. If the bottle only contained water, it might decrease bottle preference. The main goal of most is to avoid bottle introduction until the milk is well established. Then use as an occasional backup is generally accepted by baby.