screaching noise when applying brakes

I'm not trying to be con-descending, but who does your oil changes? Don't you have a mechanic that you go to on a regular basis. Back to your problem, most likely you have trashed at least one rotor or both. I would be checking the rear brakes also, before you trash the brake drums. Good luck

check your front brake pads, sounds like they are worn out and are metal to metal, some pads have an early warning tab made of stainless steel to indicate when pads are getting low this will give you a squealing sound when the brakes are applied, letting you know your pads are due to be replaced before you ruin your rotor, also a bad wheel bearing can cause uneven wear on your pads so check them as well, and last check for gravel between the backing plate and the rotor.