My car's CEL comes on every 500 miles or so and when I get the codes checked it says "catalyst below efficieny (bank 1)" I got some emmisions booster and it made the light go away for a while but it came back. Anyone have any ideas? I think my catalytic converter might be going but the car doesn't even have 70K on it

Thanks in advance.

Dark Satin Green 1998.5 Contour SE Sport V6 5-speed No ABS, No TCS, No fold down rear seat, and the list goes on.. Pioneer DEH-P6400 CD deck 220 Watt Pioneer 3-ways