Delicate to the Touch

I know that my wife's been sad that I don't seem that interested in her anymore, because I avoid touching her.  But it's not that at all.  I'm afraid of hurting her or messing something up.  I just look at her as so delicate, and I don't want her to be uncomfortable by my selfish desire to rub her belly.  A couple of times, she has put my hand on her belly when the baby is shifting or kicking, but I'm always afraid to press too hard.  I guess I shouldn't be so concerned after seeing how hard the nurse presses on her with the sonogram machine.  But I am.  Chalk it up to my over-protective instinct...even against myself.