We had BF issues from DD's second week so I used a mix of BF and formula from then on. I mainly BF but if I hadn't expressed enough for a top up or I wanted to give her a bottle feed, then we used formula. It worked like a dream! My breasts adjusted fine and DD self weaned from BF (she was down to just the morning BF and 1-2 formula bottles a day) 2 weeks shy of her first birthday