It's okay. Gilliebean is right, don't get too stressed out about it. It can cause a guilt cycle where you react to feeling bad by doing something escapist, then you feel bad about it all over again and so on and so on and so on. No need for that. Take a step back away from yourself and the world and everything and clear your head and look objectively and impassively at it all.
Are your parents and those around you the picture of health?
How do you feel about the fact that you know certain foods make you feel bad?
What kind of future do you want to see for yourself? How will you get there?
Will selfishness towards your food choices now make you more able to give to others later on? (that last one was a loaded question, since i tend to think the answer is yes).
Those are starter questions, but sometimes, when you're in a fight, you have to ask yourself a few questions- find the questions that are right for you to ask yourself. Maybe put it on paper, as writing or drawing seems to help a lot of people. Whatever format you like to make it a "solid" thought for yourself. Maybe you take photos. Who knows.
Also, food should be a pleasure, and as you get more financially independent you can look for better quality ingredients and kitchen whatnot to help you reach that very sustainable objective of enjoying your freaking awesomely delicious healthy dinner. For now, you could start an herb garden, that is cheap and easy to maintain and doesn't require much space. Get some library books on classic cooking techniques (they tend to use lots of good fats and simple ingredients) and start learning to cook. Knowing how to cook and garden are very important keys to making food healthier and more enjoyable for yourself. Your palate is always evolving, like all of your other senses, you should use it fully. :)