I had this same problem with my 9-5 Wagon at approx. 161K miles. Except, when my pedal went to the floor and I pulled it back up, I had no pressure, so you're lucky in a sense that you still had some pressure.
Like others have said, you have to explore all of the cheap possibilities first, a clutch hose with a "rub" hole or split in it, a bad clutch master cylinder, (do you have any fluid inside the driver foot well near your pedals)? After you're sure your brake master cylinder has the proper amount of fluid in it, someone needs to put pressure on the clutch pedal while another person with a flashlight looks for leaks near the clutch hose or fitting at the top of the gearbox housing, or where the clutch hose connects to the clutch master cylinder. If you're lucky, you'll find a split hose that's leaking, (that would be a cheap fix).
With my car, a prior mechanic had forgotten to replace a retaining clip that attaches the clutch hose to the clutch master cylinder, that may have been my issue, but we never really figured it out. I ended up pulling the gearbox, replacing the clutch, slave cylinder, clutch tube, clutch hose, rear main seal and all related seals in the gearbox, plus subframe bushings and more when I was in there.
You can always put an unfolded cardboard box on the ground under your car overnight to try to determine which area the leak is coming from.