Should i feel a "plop" in an egg that is around 2 weeks of incubation?

[momofthree]

I ask because my first time broody is setting and i was counting the eggs to make sure she still had the same amount and had not stolen any more. i picked up one egg and as i was turning it over to look for my pencil mark, i could feel something go "plop" to the other end of the egg.....not real hard as i was handling it very carefully...does this mean the chick inside is dead or could it still be viable?

 

[cluck-cluck]

I don't think that's a good sign. I'm on day 15+ and my eggs never felt like that, in fact, they're white, so when I look inside, I still see it's full, no air to allow such a thing (except in the air sack) Sounds weird, does it smell bad?