I'm not comfortable with my body weight?

See a Dr ASAP: Many of these symptoms: binging and purging, no menstrual periods, dehydration and low self esteem, can be indicative of an eating disorder. These can be fatal as the electrolytes in your body are depleted and your heart and other organs can be damaged. You should see a Dr for immediate evaluation and treatment. Inpatient treatment may be necessary to heal your body and mind.

It depends: If underweight and trying to gain weight or overweight trying to lose weight best would to start with your GP or PCP in order to rule out possible medical conditions and to coordinate further care to achieve your goals.