the healthier I eat, the shittier I feel?

I've been vegan for almost 3 years now and it's amazing except for one thing. I noticed that now whenever I eat something "bad", like oily or high in fat I feel sick. AND COFFEE. I used to be an avid drinker like 2 cups everyday for years and now a small latte makes me nauseated. I'm glad that I'm eating less processed foods and cooking more healthful meals but I hate that whenever I want to indulge (e.g. faux meats, fried whatever, junk food) it makes me feel soo ill :(