It's the same thing for me. I've lost 100 pounds and as I lost weight I felt fatter than I did before. Pictures help, although I don't take many. Clothes help and measurements, too. You'll also be able to tell the difference when you sit in chairs that have arms, for example. But, yeah, it'll take a while before you can see the difference.
One thing I do sometimes is to point at women on the street and ask if I'm the same size. It's always women who look thin to me and I'm always told that I'm way thinner but I have trouble believing it.