Well, where is it wet at? You have stated to us that you have had to add coolant, and that you noticed it on the driveway, but where is the bottom wet?
IF it was a headgasket TYPICALLY it does not leak outside the motor, not saying it can't, but a majority of the ones I find are leaking b/w cylinders.
Is there coolant under/around the crank pulley? Good start towards the water pump leaking, but you need to VERIFY not by hanging parts.
I mean you could go on and on, but where do you physically see coolant under the car......ON the car, not the driveway.