My 2 cents.
Are you sure it's not a ticklish spot?! I have one just above my pubic bone, and if someone is sliding their hand down my stomach trying to get to a certain spot, I might jump, but it's totally involuntary.
It's all about feeling comfortable in your skin, I think. Even though it's been a few months since I've been in a relationship, I haven't really had this issue for a very long time. I've even been able to hang out naked with boyfriends in the hot weather, or have showers together. For me, I was always just a little more self-conscious if someone was just plain looking at my naked body than touching it. But I'm over that - and plan to go to a nudist camp with a close friend of mine next summer!
But I digress. I don't really know how I got over it, but I did. Maybe I realized that this is my body, like it or not, and if you're here and touching it, it must be because you like it or you wouldn't be here touching it.
Pineapple (and others), you're so lucky to have supportive spouses or significant others (S/Os) on your weight loss journey. It is a genuinely difficult thing to do, losing weight, not just because of the personal aspect of it, but because of so many other things (that I've touched on in other threads: not the least of which is prejudice). I can't tell you that your S/O actually genuinely loves you, but if they're sticking with you through this, chances are that they do.
A hand on a stomach or a thigh is so much more than a hand on a stomach or a thigh. It's a way to communicate: to you or to other people. A hand on your thigh in a public place might mean, "Back off, dudes. This one's mine." A hand on your stomach in the dark might mean, "Wanna get freaky?" or it might mean, "I'm your man, you're my woman, and here we are, together in bed, enjoying each other, and I'm glad you're close enough to me that I can touch you." Or, "I feel safe with you. I want to make you feel safe." Or... well, you get the point.
But the bottom line is: he wouldn't touch you if he didn't like touching you. Which means that your cringeing is unfounded! He WANTS his hand to be there. Let it be there!!
Have you talked with your boyfriend about this issue? Have you told him how it feels? Maybe you could give him slightly restricted access to the parts of your body he can touch, and make some sort of game out of letting him touch the more sensitive parts like your stomach and your thighs. This could be a fun way of relieving the tension involved and might help you relax into things. (sounds a bit like cosmo... DOH!)
Or maybe if you just talked to him, he would tell you how ridiculous you're being, how beautiful you are, how much he wants to touch you NOW... and this time you'd believe him.
Good luck with this one! It's just as hard to undo self-confidence issues as it is to lose a whole buttload of weight (pun unintentional...) but it's just as worth it.
Be strong and beautiful and confident!!