I'm concerned for you. This isn't healthy man, it sounds like you might have an eating disorder. You feel shame before and after you eat, and you hardly eat, you mentally cause yourself to feel nauseous, and these aren't good behaviors. I respect your dream and dedication to be a fighter, but in order to do that and also have a good physique, you need a good health. You can definitely and should cut out the unhealthy crappy food, but you should still be eating well. Right now, try to build your calories up, don't overwhelm yourself. If you cut like this, you will feel fatigued and your progress and body will be exhausted, your body needs food for energy. In fact, you may experience muscle loss and health issues. Try not to over think about the physique; having a healthy diet, along with the fact that you exercise, means you won't really mess yourself up. Slowly increase how much you eat a day, eat natural products. Meat (inclusive of fish and poultry) , dairy, fruits, some whole grains. What can also help is having snacks, and trying liquid cals like shakes. Also try to relax and reduce stress and improve other parts of your life. Make sure you get recovery days, don't push yourself to the point where it's harmful. Eventually try to get to 2-3 full meals a day with a few snacks and hydration. I'm wishing you the best man, mentally and physically.