Pronounced "S" During Garageband Vocal Recording

I am trying to record a meditation in Garageband, but all the way through my S's are pronounced and distracting, and any time I take a breath or open my mouth you can hear it as well. Now I am not using an external microphone, so I'm not sure if that makes a difference or not. I am not familiar with the ins and outs of Garageband, and I am new to recording. Is there some way to reduce my S sounds, either during the recording or after the track has been made? Is a microphone necessary?