Ahhh I know that feeling, memang sakit hati A few of us mum friends went through this, sometimes it's the taste, sometimes they're not hungry, or sometimes the bottle/teat itself dia tak suka. Have you tried switching the brand, or even just the bottle type (like the nipple flow or shape)? Also, it helps to offer smaller, more frequent feeds instead of forcing big bottles, and some of us found warming the milk slightly makes it more appealing. But since your doctor is concerned about his weight, I'd really suggest chatting with them about this specifically, maybe they can rule out other reasons or refer you to a lactation/nutrition specialist who can observe the actual feeding. Jangan worry sendiri je, get proper guidance okay