Alexis the tiny-
I pick up on repeated references to weight and eating... someone you know suggesting you gain weight, certain days that you say you 'can't eat at all', dizziness, fatigue, and your saying that you are trying to gain weight.
Pushing one's body to 'train' and exercise more and more while not giving it enough nourishing food and calories to build muscle and maintain good health can result in serious illness that will also show effects including dizziness, 'incredible tiredness', sleep problems, getting frequent colds and flus, etc.
I hope you are smart enough to try to get further professional help for these issues and help in managing your anxiety levels. Good luck to you on your quest for wellbeing, young woman.