why is my car leaking antifreeze

you could have a pin hole in one of the hoses. you will have to pressure check the system to see if it is leaking. a garage will have the proper tools for this check.

Remove one of the front spark plugs, there will probably be water in the cylinder. There is a plastic intake plenum on top of the engine that needs to be changed about every 75k-100k miles.

Check on google for Buick Regal recall notices as I can't remember exactly but there was a recall about a plastic part that cracks and leaks anti freeze.