I own a 1997 Accord LX 4 cylinder, and my brake fluid seems to be draining extremely fast. It will be nearly half empty maybe 2 weeks or so after filling it up.

The thing is, there is no visible leaking on the ground under the car- where could the fluid possibly be draining from?

 

Look at the booster just under the Master Cylinder, see if it is wet and all the paint peeled up.
The master can bypass and let fluid out the back of the cylinder.

Back in the 80's the rear seal was different and the booster would fill up with brake fluid.