2001 Ford Escape Clutch Question

On Thursday of last week, I started noticing a clattering noise while holding my clutch in (didn't realize clutch connection to noise until Friday). On Friday, while sitting at a long light on my way home, I let the clutch out to give my foot a break. When I tried to put my Escape into gear, I was unable to do so for several seconds. Eventually I was able to get it into gear and had no more problems from my clutch that day. On Saturday I decided to test out my clutch only to determine that I was unable to put it into gear from neutral with the engine on. When the engine is turned off, I am able to put it into gear however. I also noticed that the slave cylinder was moving when the clutch is engaged. What is your take on my problem?