Ahhh I feel you! Anak saya dulu pun rejected plain formula masa starting work jugak, memang stress. Honestly, formula with flavours macam vanilla or strawberry boleh je kat age tu, tapi maybe try dulu mixing sikit-sikit dengan breastmilk your express so dia lagi familiar dengan taste, a few of us tried that and the kids accepted better. Try juga different cup like sippy cup or open cup instead of bottle, sebab sometimes diorang rebel against botol je, bukan susunya! One of my mum friends suaranya taip susu dalam porridge atau cereal first, pastu slowly introduce the formula in cup form bila dia ready.