I wonder what is your body image. Few women are happy with their bodies, but Saturn sitting on your ascendant and Chiron oppositing it could give you more body issues than most. Sun conjunct Venus can suggest that you identify (sun) with your femininity (Venus), which in our culture can mean a lot of attention to a thin body image. Is it extra important for you to feel thin, for example; or do you feel frustrated or angry about your body?
I wouldn't worry so much about eating soup for a month if it is healthily full of vegetables and protein, but if it is the same type out of a can day after day; or worse yet, a dried soup mix out of a package (high in salt and chemicals, low in vitamins) you can become malnourished.
However, I think Pluto square to so many planets, especially your sun, would make you feel that control issues are big in your life. People with Pluto square sun were often bullied as children, so they learn not to develop a lot of trust, and tend to construe relationships in terms of winning and losing. If you have internalized this "message" you may be very hard on yourself. Sometimes with eating disorders, there is a displacement of the real emotional issues bothering a person onto her body.
Eating disorders can become very serious to your health, so I hope you will make an appointment with your doctor for a check-up, and a chance to discuss your diet. The astrology will only take you so far.