Xin,
If you really wanna start weaning him off breast just for night time, you have to be very sure and be very consistent. If he rejects bottle then u straight away give breast of course it won't work or it may take him very long to learn to accept bottle again.
Anything with babies, consistency is key! Be it bfing, feeding cereals, sleep routine, self soothing etc all requires consistency. Babies don't know what we want. It's thru consistency that they learn and grasp the idea that if they don't accept bottle, they will go hungry at night. Gotta be very patient and expect a few nights of struggling etc but gradually you will reap results if you don't give up. [IMG=http://www.singaporemotherhood.com/forumboard/clipart/happy.gif]