1) Bluelipsblueveins, you are loved more than you possibly know. You may feel otherwise, others may say otherwise, and you may even hate yourself, but the truth is that you are dearly loved.
2) Stop telling yourself that you hate yourself, get rid of that self-condemnation. Instead, tell yourself that you love yourself- you may not even believe the words "I love myself" but that's ok, every time you want to hate yourself, love yourself instead. You may not be able to control everything that happens to you, nor what your mom says or do, but you can at least be kind to yourself and love yourself- this start with what you tell yourself in your head.
3) How your mom treats you and your brother, based on what you have written, is not right, and it has NOTHING TO DO WITH YOU- it most probably has to do with her! I find that when people act out against others in unkind ways, the issue often lies with the person herself, not you. It is obvious that your mother has issues she herself is struggling with. Your response is to not take it personally- do not introvert, do not ruminate on the things she's said or done, or your own mistakes (real or perceived), let it go.
4) Pick up the book The Mom Factor by John Townsend and Henry Cloud. This book will help you understand the various types of moms there are (e.g. a controlling mom, a china doll mom etc.), the possible causes and how it affects you as her child. More importantly, how you can set boundaries and heal from it. This book will help clarify a lot of things and help you realize that the problem is not you! At the same time it will teach you to forgive your mom and to also take responsibility for your own boundaries and healing.
5) Set boundaries. The book above will go into more detail, but one of the best things you can do yourself now is to distance yourself from your mom, physically if possible. You will need time to heal and discover yourself, and you can't do that when your mom is still affecting you to such a large degree. It is a good thing that you're going to college, this should create the physical separation necessary for you to heal. It will help greatly if you can find a group of friends who are supportive and able to love you for who you are, who are encouraging and kind. Take note of your natural tendency to be drawn to people who are similar to your mom, i.e. put you down, discouraging etc., and stay away from them.
6) Eat more. I surmise that you are restricting your food intake, which invariably leads to nutritional deficiencies and physiological detriment- your perception, moods, confidence, self-esteem, emotions can be negatively affected and makes it harder to recover from this situation. You may ruminate on issues far more than you should, feel low self-esteem and self-hatred far more than is reasonable given your circumstances, and find it harder to get out or fight back (like your brother does). Consequently, you may start to obsessively focus on issues like your stomach, which causes you to eat even less, and a vicious cycle begins. I was in this situation before.
Do not be afraid to eat some comfort foods- a little dark chocolate, some ice cream from time to time, will do wonders for your soul and help make the world brighter.
You will find that the as you heal and recover over time, your body will easily lose weight and become healthier even if you snack from time to time. Unnecessarily restricting your diet, however, creates stress on your mind/body and can lead to weight gain. Moderation is key.
7) Finally, all this stress, self-hatred, depression has drained your body natural resources considerably, and that is why it is much harder to recover/ bounce back from such situations.
Julia Ross has written a book titled The Mood Cure, and explains how and why when certain resources are drained from our body, our moods and perception of life can be severely affected, and makes recovery much harder.
You can take her questionnaire to see if any of the profiles fit you: https://www.moodcure.com/take_the_mood_type_questionnaire.html
Her book goes into more detail about how to recover from such moods, and I believe will be a foundational step for you to heal yourself.
Hope this helps.
In God's love,
quikfire