What Are The Symptoms Of An Eating Disorder?

I m an 18 year old female, I am 175 cm and 54 - 55 kilos, which gives me a BMI of 17. About 7 months ago, I went through my final exam period and dropped 5 kilos from stress and anxiety, initially being 60 kilos. Since then I have had an obsession with keeping the weight off and losing more and I never used to be like this. For the past month it has been quite bad. I have literally got into the habit of starving myself, feeling guilty if I even something as small as a sandwich. I will count the calories of everything. My new eating habit has turned into drinking energy drinks as meal replacement as well as diet pills. It has escalated to me feeling very disappointed if I can t go the whole day without eating. It is on my mind almost constantly. When I look in the mirror I don t feel I am thin or underweight. I don t however see myself as fat, I just see largeness in certain areas of my body that I want to go away. I am beginning to feel quite fatigued and ill, and have times where I ve felt I was going to pass out. I come from a family of 6, where everyone, except myself, is very overweight and I m not sure if this contributes to my behaviour. When someone tells me I look like a skeleton or sick from how thin I look, I take it as a compliment and it becomes encouragement to me. I know how sick this is but these are my initial reactions. From my understanding, anorexia nervosa is an obsessive compulsive disorder and is associated with extreme fear and terror. I don t have these feelings, however the idea on putting on weight is very upsetting to me. Can someone enlighten me as to what s happening? Is this just a phase or is this the early signs of an eating disorder?