DD2 is now 5 weeks old and bf has been going really well up to now, feeding on demand and she has gained over 2 lb since birth. Suddenly yesterday she has begun refusing/fussing but only on one breast. She opens her mouth to latch but doesnt seem to be able to get a seal and when she does it doesn't feel like a vacuum is being created and she pulls off in seconds. I know there is milk there as she has it on her chin even after a few seconds. Whats going on?? is this the beginning of the end for breastfeeding? I'd appreciate any advice.