I believe [this][1] will answer your question:

> If you created your account with a dot in your username and you wish
> you hadn’t, you can change your ‘Reply-to address.’ To change your
> reply-to address:
> 
> 1. Click ‘Settings’ at the top of any Gmail page.
> 
> 2. Enter your [email protected] without a dot in the ‘Reply-to address’ field.
> 
> 3. Click ‘Save Changes.’
> 
> When you log in to Gmail, you need to enter any dots that were
> originally defined as part of your username.



  [1]: http://www.nerdydork.com/gmail-addresses-ignore-dots.html