Pregnancy weight gain anxiety

I knew the weight gain thing would be hard for me bc I've had issues with me watching my weight obsessively since college. Yo yo dieting going from thick to thin to thick to thin to thick. There were times where I lived off of Diet Coke and pop corn and working out 2hrs a day and after every meal. And I revert to those old habits when I notice the scale creeping up. Well its not creeping it's running leaps and jumping hurdles and my anxiety is starting to kick in bc I've never seen my body like this... yeah yeah I know I'm crazy as hell. Yeah yeah been there done that but it's now affecting my decision on whether I want to breast feed or not, for fear that I'll have to eat more to sustain a steady milk supply and it interfering with losing the weight as fast as possible through intense work outs and a low calorie diet... any advice from non first time moms who have previously breast fed. I know it's healthier for the baby, but I have to be a mental participant, and I don't feel I can do that if I'm not happy with the way I look. And on top of that I gain weight when I'm sad. I feel bad for thinking so shallow but it's my truth.