Ahhh I know macam mana perasaan tu! Anak saya pun macam tu around that age, tiba-tiba reject bottle padahal before okay je. A few of us mums noticed it's quite common around 4-5 months, and honestly sometimes they just go through phases. Try nak warm up the milk sikit, or ganti bottle teat dengan yang lain texture (some babies picky about the flow), and buat sure bottle cleaned properly sebab dia boleh notice different taste. If nothing works, jangan stress sangat, some babies just prefer direct feeding la, so maybe try express milk and give cup or spoon for a bit, then attempt bottle lagi later. Fingers crossed dapat breakthrough soon!