Not charging with headlights on

Ok what you did means the alternator is good.

Now you can take it a step further and check the regulator wiring. Remove the regulator, and jumper the two regulator wires together. This, essentially, does the same thing as connecting the field terminal to battery. Run the car long enough to see if it charges.

If it does, double check absolutely sure that the regulator is well grounded, and replace the regulator.