Lulu I had huge issues with this too, unfortunately for me it lasted almost three months! I suspected bad wind/tummy pains as sometimes she was overtly uncomfortable, continued crying after a took her off and also during this period she was very burpy and spewy. Other times however I think it was simply that she wasn't hungry enough. The biggest lesson I learned (and I still need to remind myself of it now) was to trust my baby knew when she needed more milk and she would take more then. And also not to clock watch. DD was slowly transitioning from 2.5 hourly feeds to 3-4 hourly as can happen when they get older but I didn't know that so I was freaking out at both the duration of and time between feeds. Jennifer here on the forum told me not to think about time between feeds and I also read a great guest post on the Kora Organics blog about this... Babies at the 4 month mark changing their feeding patterns and mamas freaking out about it but it's normally normal.