Why do i sometimes talk with a british accent when my parents don't?

Its normal. I sometimes sound like I have a Chinese accent because I happen to pick it up from some places. I used to have a temporary British accent because I spent quite a bit of time at my friend's house, whose mother is British. You know how british people when they ask questions the tone is different? (I can't put it into better words, sorry.) I do that. Anyway, sometimes you pick it up from people, and sometimes you just, well, do it.
Hope this helped~