Agreed, if the clutch master is leaking it'll run down the pedal and possibly leak on your left foot (mine did). Given that you're intermittantly adding fluid to your clutch master and you have fluid leaking down your pedals, then it's very possible that the master is leaking. If you still can't build up enough pressure to work the clutch after adding fluid then you'll probably have: a) badly worn master that needs rebuild/replacement in order to work again, b) slave leaking too, or c) both.
I suppose it's also possible the throw out bearing is on its way out too, but I'm only saying that to try and cover as many possibilities as possible.