you're 18, so I presume you can cook for yourself? and use vegetables? couldn't you just not eat the pizza and cheesy pasta?
anyway, more on topic, not vegan, infact many many years before that (they may be boring):
I was about, 10?11? and my brother (about 19?) started boycotting nestle, whilst home, he told me about it.
Well I started boycotting to, mum would say "just finish what we've got left in the house and I'll not buy it again, don't waste it" I'd finish the nestlé item, and she'd buy it again, after about 3 times I just stopped having it and said "fine I'll waste it, better then you buying it again" (or an argument similar to that).
Amusingly now he says he boycotts nestle still (I still do) yet he eats after eight and drinks buxton water

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another story, not a problem. I turned vegan, then my collar bone went snap (due to judo) and my mum decided I wasn't getting enough calcium and that was why. Perhaps it was part of the reason perhaps it wasn't, anyway, I end up seeing a dietitian (a few months ago) and telling her where I got X Y and Z from, etc. every 5 seconds she was turning the page in the text book and realising yes, I was, and just ended up telling me to eat more mushrooms

(not really a problem, although I should get some more in thinking about it). I found it crazy that I was telling her that I got calcium from spinach, as well as iron, and the same from broccoli, and she had to check it because she didn't know.