Finding your authentic voice is a difficult thing for many writers online. It takes time patience and an understanding that blogging is not performing, atleast for most people.
Liz Strauss understands this well, and has put up a great list of steps to achieve your authentic writing voice on Successful Blog.

1. Tell your own truth, but don’t think that doing that is special.
2. Write simply, using the words that you think with.
3. Care about one reader – real or fictional.
4. Until you know your authentic voice well, read what you write aloud and change it until you could easily say every word without tripping.
5. Use metaphors and stories to be sure that your message is clear.

There is much more great information on the site, so be sure to check it out, even if you don’t think you are struggling to find your authentic writing voice.