It's 2 things:
1) Normal
2) FRUSTRATING!!!!
I've lost about 45 pounds and I've only lost 1 pant-size, or roughly 2-2.5inches...everyone is different, your results are fine. It's not going to happen overnight......
Stay the course, it is what it is, don't worry about it and avoid having sexual relations with Brittney Spears. (Just had to throw that in for good measure)
Seriously, you don't have a choice.......just keep up the work and it will happen in time. So long as you don't have a huge protruding gut, you'll look fine even if you're waist is larger then average. We're all build different. If I were to guess, I bet you have bone just under the skin around your waist, eh? Again...keep up the good work, don't fret over your perception of a lack of results and keep movin'