You either have a crack n the block or a head gasket problem. Bad head gasket can be fixed, cracked block = new engine time.
In a 2008 car you should not be running into problems like these unless you let it overheat before, ran it low on oil, or was "racing" the car and keeping it at redline.
You are going to need a mechanic and hope it is just a head gasket and that it will be less then $500.