how do I deal with this

My bfs parents do not support me or my goals at all. They always have rude comments and think I am crazy. I am going to school to become a doctor (8 year plan). I am only 20 so I don't see and issue with it I am motivated and work hard. They think it is crazier how long I am going to school for and think I won't ever get married or have kids. My bfs parents are rubbing off on him. Although he is supportive I know they have told him their idea. I honestly think they want me to just sit home and clean/cook. That's not me at all! How do I stand up to them/ not let them bother me? Shouldn't they be proud that their son is dating someone so ambitious. Most of bfs cousins are poor, had kids young and live with their parents, wouldn't that make them realize how important an education is for me?