I feel a bit childish

I know that being eighteen means your are legally an adult, and as an adult you can do whatever or whoever you want. But I have a problem. I went to Georgia to spend a few weeks with my aunt, I met my second cousin's friend, he's nineteen. We started talking and joking with each other about our family and our race. I told him I was a forth black, a forth german, and one half american Indian( Cherokee, and Siox) He said he would do me and we both laughed then he asked me if I would do him. I smiled and said yeah, just yeah, because I thought we were just pulling at each other. He coaxed me to go outside with him and he made a move to kiss me. I told him I didn't know how to kiss, he said it was okay. We kissed, and after a bit more talking and kissing I gave him my virginity. I now feel like a child, lost and confused. I don't know what to do. I feel dirty because I liked it. Help please.