Although it's certainly possible I've swapped a pound or two of fat for muscle, I don't tend to "bulk up" easily, so I'm not one of those people who gains a lot of muscle. (Actually, I used to be so frustrated that I would lift weights but not build any muscle, that's one thing that did improve somewhat after the radioactive iodine treatment.) And my clothes aren't any looser.
Believe me, I've thought of every possible rationalization for why the scale wasn't budging, but after 2 months of frequent tough exercise and excellent eating habits, I'm facing the fact that something more has to be going on here. (I have food diaries from the last time I lost weight, so I can easily compare what I ate and my workouts then versus now.)
I know how hard it is to exercise with a baby, but if you have room in your apartment to do an exercise tape, that's one possibility. Don't forget part of that 15 lbs. is in your bra