One belly and one question

Okay, so I've gotten to almost 19 weeks and have posted exactly one belly picture. Well, what can I say? Here's another one, taken at just over 18 weeks. I still find myself holding in my abdominal muscles. I try to force myself to relax, 'cause it's obviously not doing any good, but there's just something about a big ol' belly hanging out that makes me tighten those muscles. Am I just a freak, or does this happen to other people as well?

The question part of this post comes from my husband. I am fully aware that everything I am about to type is going to make me sound insane, but he asked me very nicely to pose this issue to my faithful readers, and I promised I would.

The thing is, we have a ticklish couch. It's true. If J tickles the couch around me, it makes me squirm and giggle. We thought it was just me, but when my stepdaughter was here for her Spring Break, she reacted the same way when he tickled the couch with both of us on it. She is now trying to blame me (apparently she thinks she had a bout of sympathetic giggling??), but I'm pretty sure it's the couch.

J also tried tickling my MIL's loveseat when my stepdaughter and I were seated on it, and it didn't have the same effect. So, clearly it's our couch. Right?

Now, the part he doesn't understand is, all three of us (my stepdaughter, J and I) can tickle my actual belly (in an attempt to tickle the babies' feet, of course), and that has no affect on me whatsoever.

I believe his question is, how is this possible? How is it possible that him tickling the couch I'm sitting on makes me collapse with laughter, but him tickling my actual belly does nothing but make me smile?

I don't have an answer for him. If he doesn't believe that the couch is ticklish, I don't know what I can do to convince him.