With my cringe username, let's just say I hunted and hunted- and I couldn't find a way to do so. I even reached out to what I think was the webmaster when I came back on here via the contact us button at the bottom of the site. No reply, but that could be for any number of reasons(idc anymore, it's growing on me lol).
Thankfully my username isn't related to my real name, but considering rule 8 of the forum, I can see why you're uncomfortable having it on here!
Maybe a mod with the power to change it will be happy to help(idk if any of them do- it might just not be something within the site's parameters), but it might be one of those instances where you might feel safer to starting a new account and deleting your old one.
For what it's worth tho, I wouldn't have guessed it was your real name. Some people combine words, others will use a first or last name and something else meaningful to them, references to actors/actresses and other such things. So if you decide not to stress about it in the end and, I don't think it'd be that big of a deal.