If it's engaging at the top, it's likely time for a new clutch. Failing hydraulics will not allow -disengagement-.
A similar condition to what you describe can be caused by a well worn throw-out bearing. If once engaged, the clutch doesn't 'slip' it points more to the T/O bearing, but it's best to do the whole assembly at the same time: Same amount of work, and the piece you don't replace WILL fail sooner than later.