Hun, it could just be that she's approaching the 12 week mark. You'll find plenty of threads on here about 3 months old being fussy at the breast. It's extremely common - they start becoming so aware of what is going on that they don't want to take the time to finish a feed. Some mums find a breastfeeding necklace works well, and also feeding away from distractions. As difficult as it is though, she is probably drinking more than you realise. As long as the wet nappies keep coming she's getting enough. And this too shall pass