How to tell my mom how I met my boyfriend?

I met Joe on Chat-roulette back in November. We met in person in March for the first time. Before then we had become rather close to each other even though we hadn't met. After we met we had hit it off right away and felt true affections for each other. As cheesy as it sounds we had fallen in love before even meeting in person. My mom knew about him from my phone bills and had noticed him on Facebook and that we didn't have any mutual friends. Joe asked me to be his girlfriend back in March when we met. Since then we have visited twice. He lives in NY. He came to visit me twice and I recently went to NY to see him. I am 19 years old and still live with my mom. Somehow she figured out that I had met him online. She does not know how though. I don't want her to make assumptions as I know she has. I wasn't doing bad things on Chat-roulette and I am afraid she will look it up and see bad things cause that's what some people do. I was just on there to talk to people and Joe popped up. Joe and I want to try and make this relationship last for a long time and perhaps it will be a life long deal. I just don't want my mom to think the wrong things. A lot of people meet online these days and make it work, so I am hoping I can surpass the bad judgment.