Why do my D, E, and F keys not play correcty on my alto saxophone?

When I go to play my saxophone and play from c to d and hold down the octave key and press down the keys at the bottom of the saxophone, the d comes out, but sounds horrible and as if it is a high g or a. If you need me to clarify this a bit, please ask, but if you can help, please do. I appreciate it. Thanks.