Help! i think Buddy, my leopard gecko is dying. advice asap please ):?

It sounds like mouth rot. Not MBD. Mouth rot is caused by poor living condtions aka low temps not cleaning the poop everday. MBD is where there still eating just have disfiguring bone twist. Mouth rot is normally caught when its at your stage with the eyes. Most new owners dont catch the very early signs of not eating and black mouth. You need to get him to the vet and they give you antibotics its really cheap. If you dont im afraid he may die.