Karyn - I had the same problem that you're experiencing.
I honestly didn't know what was skin and what was fat until I talked to a plastic surgeon. All my deflated skin looked exactly like cellulite to me because of the way it was all wrinkled up. One thing that was a tip-off (this is going to sound gross) was that the skin would float in the bathtub. Yuck, right? But that's one way I could tell that it was skin and not fat. And I could grab handfuls of it. Double yuck.
When I went to see a PS, he told me it was skin, ALL skin. He told me that I had YARDS of skin, even though it looked like fat. Huge relief! He took his hands and circled them above my knee and pulled up, like you'd pull up pantyhose. And it all pulled up and smoothed out! I highly recommend going to a PS for a consult for your own peace of mind, even if you don't think you want to do anything about the skin.
About body fat and excess skin - I worked with a trainer in my gym while I was losing weight and he took my BF every four weeks with calipers. He was able to distinguish between fat and skin - perhaps Mel can talk about how that's done. So yes, I think that a qualified person can do your BF despite any loose skin. One word about BF and skin, though - the lower my BF got, the worse the skin looked because there was nothing filling it out. It's not a reason to stay fat, of course,
but it's something to be aware of.
The whole excess skin issue caught me completely by surprise when I reached goal. Crazy as it sounds, I really felt like a failure because of how I looked at goal. That's why we put together the skin FAQs sticky here in Maintainers. So please don't apologize for asking questions - that's what we're all here for - sharing our problems, questions and experiences.
Extra Skin vs. Flab/Fat
I'm just brimming with questions today and who better to turn to than you girls!
Pre-tummy tuck, it was very easy for me or my trainer to get a caliper reading on my abdomen. Now it's near impossible. I don't know if Meg has had the same experience. One the other hand, as long as my pants fit, I no longer care.
I'm feeling like the Bionic Woman or the Terminator or something ... Or else the cat ... 
