BFing and Exercise/Diet

My little girl is 7 weeks old and I'm trying to start losing the baby weight. I have about 45 pounds until my desired weight goal and dont have a clue on how to start. When I started working out with my first born, he immediately weaned and stopped breastfeeding. My sweet girl is too small for me to even think about that happening so someone please tell me what foods/exercises helped you lose weight without tanking your supply!! Thanks in advance!