2001 Pontiac Grand Am Leaking engine coolant

My car continues to leak coolant. Although, I cannot see it where it is parked, I can smell it when I get out of the car. The low coolant light came on and I checked to coolant resevior and it was empty. I filled it up and took it in to the mechanic. He stated that I had leak in the water pump and the housing around the head gaskets had a crack. All the was replaced. Drove it for two days, low coolant light came on again. Checked engine coolant, completely out again. I cannot figure out what else is wrong. The car has never run hot. When the fixed the crack around the head gasket housing, they also replaced the tempature valve according to the invoice. Where else could it be leaking from? I check it every other day and have to put more it, it is never completely empty but is low. Please advise. I can't afford to buy a new car right now, but taking it back for the same thing is getting very annoying. Can you advise what I should look for now?