Bulimia. A terrible cross to bear. Glad you are in therapy. Are you seeing a dietician or nutritionist? If not, you need to. They will help you understand portions and meal planning.
A word of advice.. Stop looking at yourself through other peoples eyes. Do not let them influence how you feel about yourself. Your weight is not their business.
Bulimics tend to start out with their disorder being all about weight., but it ends up being about stress management.
Depression, anxiety, anger control issues, ptsd.. Are all part of it. But, Dissociative identity disorder is a very rare psychiatric disorder and I doubt that you have that. A counselor or therapist is not qualified to make a diagnosis like that. You know that.
Keep a food diary. Write where you ate, what time you ate, and how much you ate, then write down how you felt about what you ate and whether you purged or not. Then write down what was going on before you ate. That way you can look for patterns or triggers.
Use distraction techniques. When you feel the need to purge after you know you have eaten a normal healthy meal.. go for a walk, call a friend, chew mint gum, eventually the need to purge will pass. Keep a tooth brush and bottle of mouthwash by the kitchen sink and brush your teeth or rinse your mouth. Don't do this in the bathroom.. Its to handy to the toilet bowl.
If you want to scare yourself. Look up pictures of people who have died from esophageal and stomach ruptures from throwing up. A very real possibility for a bulimic. Nasty way to die, with your face in a toilet bowl.