1999 Chevy Cavalier car leaks antifreeze replaced water pum

Engine Cooling problem
1999 Chevy Cavalier Automatic 147000 miles

I have a 99 chevy cavalier and more than a year ago I replaced the water pump when the car kept leaking antifreeze. I have also had a new engine put in and replaced the the power steering pump or something with the power steering. Anyway the car has started leaking antifreeze again. At first the warning light just came on so I just put some more water and antifreeze in and it was fine for almost a week. The one day the light came on and wouldn't stop but the temperature gauge didn't seem to get 2 high. After giving the car some time to cool I found a huge puddle of antifreeze under my car. I filled it up with water and it has been fine since. O and the air conditioner doesn't really cool. If the fan is on and set to blow cool then it will but not the ac. What could be the problem?