As long as you are not doing so to defraud someone, you can use any name you wish to. The name on your birth certificate is your birth certificate name. It is also a "legal" name, as is your married name you have used for so long. A man named Robert also can have the "legal" name of Bob, Roberto, Rob, R, Big R, etc. I do not see why you need to undergo a name change. You do not tell us what your problem is that makes you want to change your name.
