Sorry for such a vague description...

I remember parts, such as a hidden society(sort of like the movie "the villiage") that would never experience pain or sadness, they had a medicine or something for it.
A child drowned in a river, they repeat his name through out the day, starting loud and grow quieter as time passes.
The main character somehow learns to feel pain, from dreamlike experiences that include sledding and breaking a bone, and being burnt.
At the end the main character escapes from the town with a baby that was born with a twin and supposed to be killed.

It sounds a lot like The Giver by Lois Lowry, especially the twins and running away at the end.
Look up a summary of The Giver that may be what you're thinking of.

Yeah I'm almost positive this is the right answer