They probably traced your IP address.
And if that's the case, STAY AWAY if you don't know them. Engaging them in any form of communication will only encourage them, and may cause hacking attempts on your computer... or worse.
Unless they are a moderator, they can't get your IP address from this forum.
The Internet is not like what they show on TV. You can't just say some gibberish, throw down some random commands into the command prompt, and hack your way into your neighbor's bank account and get the IP address of some random guy on some random Internet Forum who you've never connected to elsewhere.
You gave out your full birthdate, gamertag, and the city you are living in. With that much information, a determined person could track you down.