Ang 4 months is actually perfect time to start, kaya maganda timing mo! Start by introducing the bottle gradually, maybe one feed a day lang at first, then dalawa, habang patuloy mo pang siya breastfeeding para hindi ma-engrage ang breasts mo. A few of us tried different bottle nipples kasi ang babies ay choosy talaga, some prefer the wide ones, some the narrow, so hindi lang mag-give up agad if baby rejects the first one you try, okay? Warm the milk to body temperature at let daddy or someone else give the bottle first habang wala ka muna, kasi ang babies ay alam nila kung mama or hindi ang nag-aaya, haha! Patience lang talaga at consistency, mama, give it a week or two bago ka mag-worry na ayaw talaga ng baby.