I am currently taking adderall , 10mg am 15 mg pm , now my doc added prozac (fluoxetine) . i am terrified of gaining weight. is it likely i'll gain weight ?

No, not necessarily.: If you are worried that you might gain weight as you start Prozac (fluoxetine) ( you may be surprised to see that you feel like eating less on the prozac), take a proactive approach. Watch what you eat, maybe keep a food log, try a low carb diet by eating only fruits and vegetables as your carbs and cutting out bread, pasta, etc and eat more protein and "good" fats, and start more exercise --to prevent wt gain.