Car Problems 2000 Dodge Charger?

ok it struggles to idle because the RPM's fluxuate. Also the RPM's fluxuate at running speeds. Day to day the problem is getting worse but the severity varies. The cerpentine belt does need to be tightened but I doubt that's the problem (but I'm no expert). The car has never died on me (yet) and never had issues starting. And and in addition when I hit the accelerator (sometimes even when I don't) the engine seems to choke. Anyone have ANY idea what the issue might be?