Listening to your own voice in a different language takes time to get used to. As with most skills, the more you practice, the better you get at it. Reading Spanish out loud will help you get more familiar with the sound of your voice in Spanish, talking to a native Spanish speaker will also help, as they can provide instant feedback on your pronunciation, plus, if they're able to understand you, it means that you're doing well!
Watching TV or videos in general in Spanish is also a good technique. Not only does it teach you how to pronounce the words, but it also shows the intonation and structure of the sentences in its most natural way.