Paleobird might be on to something. I have a radical idea:
Einkorn is the Ancient form of wheat, one of the strains of wheat that they believe was eaten by the people in Biblical times. Tell mom and dad tht you want to eat wheat the way they did in the Bible. Tell your parents that you want to cook and bake your own food so you can be independent. Then ask if you could make your bread out of special flour. The advantage is that it has a lot of the germ and bran removed, so it has less of the bad anti-nutrients. It's not the modern crap which causes the problems. And it's expensive so you'll eat less of it altogether.
With your parents around, you probably can't go full Primal. But if you swear off the Twinkie junk and at least stay away from modern wheat, you should be able to get most of the way there. You're so young that being non-primal won't do permanent damage. You have time.
5'0" female, 45 years old. Started Primal October 31, 2011, at a skinny fat 111.5 lbs. Low weight: 99.5 lb on a fast. Gained back to 115(!) on SAD chocolate, potato chips, and stress. Currently 111.