I have the same problem! I've lost 26 pounds to date, and I don't see it when I look at myself. Also since most of my jeans have some stretch in them, I don't notice a huge difference in my clothes either. So every month I take a picture of myself in the mirror (neck down, sans clothing, so I can inspect fat rolls,

) and I've been able to see some difference there. It's easier to be objective when I don't feel like I'm looking at, well, ME.
I think your mind gets so used to seeing yourself that when you look in the mirror, your mind sees your face and says "oh, that's me" and fills in what it remembers previously. It just takes awhile for your mind to catch up to the new image that's actually there! (I read this somewhere, I swear...)
Just take heart that you ARE losing weight, and there IS a difference, and you'll see it soon!