I can't hear callers unless I'm on speaker phone??

It's very likely that your receiver (the speaker piece at the top) is clogged with some sort of debris. You can purchase blue tack putty to try to remove any debris from the receiver as well as the microphone and speaker in the bottom grills.

If the receiver is not clogged, then it's likely beginning to fail or is already failing. I believe your particular phone model would require a screen replacement for this issue if it's hardware related.