Try searching for audio editors that allow "formant shifting."  This will allow you to change the pitch of your voice without making it sound like a chipmunk.

One of the better ones is Melodyne by Celemony, it's easy to use and works very well.  Unfortunately its pretty expensive, though they have a demo for download on their website.  You can't save with it, but at least you'll have an idea of what's possible.  I'm amazed at how convincingly I can alter my voice with it.

The lower end editors are likely to give poorer results with more distortion.

If you don't have the budget, search for editors that allow formant shifting, but if you need very good results then you may have to shell out for something more pro.