I think part of it may be that clothing size changes are not linear. For me for example, I've lost about 50 lbs so far (on a combination of low carb dieting + primal for the past month or so). It seemed to take forever for me to go down to a size 14 from a size 16 and a size 12 from a size 14. But now I seem to be losing a clothing size or two ever 8 lbs. I went from a size 12 to a size 8 in only the last ten lbs or so. If you think about it, this makes sense in terms of a toilet paper roll: when you have a huge new roll, a few sheets don't really make much difference to the size of the roll. But when you're down to the end of the roll, taking a few sheets can dramatically decrease the size of the roll. So maybe you're at that last of the toilet paper stage? That plus because of your exercise, that 5 lbs loss might correspond to a significantly great fat loss of course.