Lately I've been having some noise from my drive chain. The best I can describe it is the sound when you ride of a bunch of those little tiny gravel bits from the road. It's pretty faint, but it's noticeable. I can't exactly pinpoint what the problem is. My cranks are tight, my lockring is tight. I figured it's either my BB or my chain.

I think it is the chain because another thing I noticed is that when I start going really fast I hear a bit of creaking coming from somewhere down there, and then when I get off my bike my chain is significantly more slack. It doesn't look like the rear wheel is slipping on the ends or anything.

The bike is new, so is this just the normal process of breaking the bike in, or should I be worried?