I don't know what I want to be when I grow UP!help!?

I'm 14 this october and my parents keep badgering me about what I want to do when I grow up and what I want to study when I'm in university.I would really like to study arts.like those stuff related to acting and singing and the media or even backstage stuff.I think my parents want me to study stuff like engineering or something related to business.but I don't want that.I'm a really creative kinda person.I design clothes,I sing,I dance and I can act really well.I'm really into the arts but I don't know if my parents would approve.I've tried telling them I'm still young and I can decide when I'm a bit older but my dad keeps saying that means I don't have an ambition and that to achieve something you need a plan and all that.and when I say I'm too young he just says I'm just kidding when I say I have ambitions and I want to attend University and he keeps judging my personality saying I'm a slack.my mom's so much better and understanding but my dad's is getting extremely irritating.what should I tell him so he would leave me alone?And what should I do when I grow up?help!