Congratulations on your loss!!! Way to go!!!
The reason could be, as RA said, that it's "spread out" all over your body so it'll take a little longer to lose some serious inches. Also it could take 15-20 lbs to drop a size. Don't get discouraged, you're doing great!
Maybe add some more resistance (weights) to your exercise routine to build more muscle, which is denser, and burns more calories than fat.