Non vegan family

I want to go vegan so bad. everytime I eat meat I feel gross out. I just don't like it and I don't want it. But my dear older sister and dear grandmother find that too much. and keep talking about I won't have my protein. I skip on meat and throw them away. I am 16 and they youngest in the family by the way. But when I go to eat out I can't say I won't meat and will force me to eat. In my school I can't find vegan alternative at lunch. How can I start. What should I do to make them believe or support. How can I eat vegan at school? I need help.