loose bottom bracket
 

I have noticed that my bottom bracket has become slightly loose as I pedal. I was wondering if it could be the bearing or does it just need tightening? The bike is relatively new with only 750 miles on it.

How about giving us some more information instead of just "my bike has a problem, help me".

Most likely, it is loose. There are a few predominant types of bottom brackets, so it'll be hard for us to diagnose or develop a fix.

My bike is an 06 TREK 1000. You can take your hand and move the crank and right or left and there is just the slightest bit of "play". I know that it is in the bottom bracket because that is the only thing that moves when I do this. The pedals, clipless, and the chainring are stationary. It is something that I just recently noticed during my last ride.

Try tightening it up (special socket required), bearings should not be shot as a BB is good for many miles.