It's VERY normal. We carry a lot of excess water weight and that's one of the first things that get flushed out when starting a weight loss program, which is needed and is fine.
Yes, it more than likely WILL slow down. Be prepared for it. You keep plugging away and plugging away and chipping away at the pounds and each and every excess one WILL come off - eventually. FOCUS on the good eating behaviors and the scale (your body actually) will in turn take care of the rest. In other words try to not sweat (focus on) the numbers so much. It's all about focusing on the behaviors. Getting these new and healthy habits ingrained in us.
And don't worry about when you hear people say that it's health-iest to lose 1 - 2 lbs a week. That's for *smaller* folks. When starting out at heavier weights, like I did, those numbers are irrelevant.
Keep up the great work. I look forward to hearing of your continued progress.