Has anyone ever used both formula and breast milk? Sometimes my in laws would like to watch her and I dont have a huge stash.. or sometimes she'll eat and still seem full but I won't have anything left... could I just give her some formula? We supplemented in the beginning and she did great with the formula we used. Also, sometimes my husband wants to watch her while I go to dinner with a friend or go to the grocery..would she be fine to mainly have breast milk and occasionally have formula?