Are you weighing and measuring or eyeballing your portions?
I have to agree that 1 lb a week is on the slower side at your size, so if you are weighing and measuring and are really sure you are only eating 1500 calories, I'd consider lowering a little bit to see what happens, but I'd also think about checking with your doctor and making sure that thyroid, Vitamin D levels, etc. are all ok.
And it's perfectly healthy to lose more than 2 lbs a week, esp. at the start. It may not always be doable, but it's not unhealthy to lose more quickly than that, and recent studies show that losing weight more quickly has no relationship to whether or not you keep it off long term, or it may even be related to losing more overall and keeping it off.
http://www.forbes.com/sites/matthewh...le-white-lies/
http://www.livescience.com/9907-surp...t-quickly.html