thermosat not working and losing water and antifreeze?

I have a corsa 2001 1.2 sxi and the thermosat isn't working so i had a new one fitted and this isn't working either, the temperature gauge is going up when i'm driving and the engine fan is coming on when the car is being driven and when the engine is swtiched off, also i have to keep putting water and antifreeze in the car, please can anyone help x