I guess you have three options. You can either continue to use your Vietnamese name, I'm sure English people could learn to pronounce it. You could try to find an English name that sounds similar to yours. I'm afraid I don't know how your name is pronounced so I can't help you on that front. Finally you could just pick an entirely new name an use that. You could be Lucy, Abby, Sophie or any other name you want; sounds like great fun to me!