Losing weight while breastfeeding

How can I lose weight while breastfeeding? I just had my picture taken with friends and I actually cried when I saw the picture. My son is 6 weeks; I gained about 60lbs during my pregnancy and I’ve lost 30lbs from delivery and swelling going down. I feel very depressed and sad and I feel I can’t be a good mother if I am too busy being sad and crying over my weight. I don’t want to be selfish and stop breastfeeding but I am getting desperate. How can I safely lose the weight? I did try to diet and I lost my supply for a few days so I don’t know what to do. Help please!