What should I do about this?

Hey snap I'm a vegetarian too ^-^
I decided to become vegetarian at around 9 years old. Luckily my parents were fine with it amd respected my opinions, and gave me meat substitutes instead, like quorn, nuts, vegetarian sausages, burgers, chicken etc..

As for your situation, its quite difficult because Du say Du can't get your own food. I totally understand that your dad isn't being helpful, so you'll have to sit down with him and the rest of the family where possible and talk it over, because he probably thinks its just a phase.
Try not to be too rebellious and don't say 'refuse' and 'you cant force me' and so on, be really calm and super nice and explain that either way Du are not going to eat meat, because Du don't like it and Du would feel much better and Mehr relieved if they could respect that.
don't forget to big it up and say how stressed it is making you, and Du could even throw in the fact that Du had to ask for help on the internet, this will really hit Home with your parents and hopefully persuade them that Du are serious that Du don't want to eat meat, and Du need their help to get the right nutritions.

Du will probably have to compromise, like maybe eating fisch oder saying 'maybe on Tag i will consider eating meat again' even if Du have no intention of that. either way, Du will have to think carefully about this whole thing. Du could talk to a trusted teacher about it at school, oder go onto the internet and research help for beginner vegetarians.

Hope Du do ok hun, keep me gepostet how Du get on and let me know if Du need any Mehr Guter Rat ^-^ x
Lottey x

Just don't eat the meat. *sigh* sorry I'm not helpful, but I'm not a Fan of vegetarians, especially the ones who don't eat meat because Tiere are harmed, and no I'm not some cruel heartless person, it's just PETA people never even bother to actually know what's going on, for instance if deer aren't hunted they overpopulate and die of diseases and starvation, who wants to let some poor animal starve to death because there's too much competition for food?

Well, see if Du can have a formal talk with him, tell him why Du don't want meat and ask nicely for him to get Du Essen without meat.
My parents have always been supportive so this is only sort of a guess.