How come nobody ever believes in me?

The people that should believe in me the most, don't. Like my friends and family. When I was younger I wanted to be a doctor, and I told my parents and they just scoffed at me. My dad even said I should just work at a bar, and that really hurt my feelings... I actually get A's in Science too, but this fact seems to surprise people. They were handing out academic awards at school, and I was worried about not getting one. My two best friends were telling me that you had to be smart to get an award. I did get an award, and they were completely shocked when I told them. When I tell my friends and family about what my dreams are, like what I want to do when I'm older, or what grades I want to achieve at school, they just mock me or tell me not to get my hopes up. And if I actually achieve something, they're surprised! I thought they were meant to encourage me and believe in me, but they don't. Why? :(