Ok.....the past couple of weeks my transmission or something in it has been acting up. When I back my car into my driveway, I hear a knocking sound coming from the clutch disc area. I was on the highway at about 70 and shifted from 5th to 3rd

. After about a sec. shifted to 4th. Now while driving all I hear is a whole bunch of knocking sounds...like something being tossed around in the clutch area.
It only used to do it while backing up...now it does all the time, and sounds worse. Also, while shifting to second, it sounds like something is chafing against something else.
I think I know what happened. But I'd like a second, third, etc., opinion. I'm ready for the worst.....lay it on me!