2000 Chevy S-10 catalytic converter

Converter had been making a rattling sound for about a week. Thought it had broken up inside, or a pebble had gotten caught in surrounding shield. Couldn't get it off to eyeball inside of it. Suddenly the rattling stopped (although if I get under the truck and bang converter with my fist it still rattles). I noticed almost immediately that the truck had lost power especially from 35 mph on up, and I think my gas mileage is going down. Could pieces from inside converter be blocking exhaust flow resulting in loss of power or is it more likely a coincidence?
Thank you in advance.