Coolant leak and overheating

[lxtn64]

2005 BMW 325XI. 206K miles.
After driving for about one mile, coolant/antifreeze start to leak and car overheats.
Some have suggested head gasket problem.
Some suggested I replace Thermostat and or Waterpump.
Does not overheat when warming car up.
Love this car, but will have to get rid of it if its going to cost me too much to repair.
Any suggestions.
The scan code show Catalytic converter problem.

[ramm440]

Look around under the hood by the expansion tank, the hose connections to and from the waterpump and all other coolant connections. You will see white dried up coolant droplets somewhere if it's leaking externally.
How much coolant are you adding and how often?