What is screwing up my cooling system?

My 2004 pontiac grand prix gt has been running hot. Need keep filling over flow. Replaced thermostat. Waterpump froze while driving and seized mr car. So new water pump now and its still getting hot. Started over heat on way to work. Pulled over had put water in overflow. Has been sitting at my work for week. My over flow is full but my radiator seems to be empty? And it looks sludgy