they happen to most of us. The first major one usually hits sometime during the first month post-op. We call it the "three week stall" because it's most often the third week, but not always. mine was weeks 2 & 3.
they typically last 1-3 weeks, but I've heard of them lasting longer (although USUALLY 1-3 weeks), Just stick to your program and stay off the scale for a few days - and know that it WILL break.