Here's the test: begin petting your dog with mid-range pressure. Does he/she do one of the following:
A) Solicit more petting by climbing on you
B) Roll over belly up, lick lips, yawn or look away
C) Energy increases and begins jumping off you
D) Moves Away
E) Some of all the above
Well then your dog probably has some touch sensitivity. Many dogs have touch sensitivity; far more often than people would think.
So one of the things we practice in puppy class and beginner class is touching your dog while feeding him/her. Many people do this exercise once in class and then forget about it. They usually concentrate on stay or leave it or loose leash walking. While all those obedience skills are important they definitely don't outrank having a dog that not only accepts touch but enjoys it.
If your dog enjoys touch you'll find him/her easier to praise/reward, spend time with, handle for grooming, handle for exams, handle in general, accept children who touch harder and inappropriately, and less likely to bite when in pain or taken by surprise. All of those things are crucial for pet dogs.
The good news is you can teach dogs of all ages to enjoy touch more than they already do. Take their breakfast or dinner and use it to teach handling. Get your dog eating out of your hand at a reasonable pace and then add touch. Make sure the dog continues to eat. The moment he/she stops eating take your hand off their body. Start with gentle touch using the back of your hand and then work up to pressure and specific handling (think picking up paws). As long as the dog continues to eat then continue to handle.
This is what we would call Classic Conditioning to teach an animal to accept something they might not like. You combine their food (basic necessity) with a small level of something new or not enjoyable and then slowly increase over time. If you were handle then feed you wouldn't get the same result.
Try this exercise a few times a week for several months and watch the changes in your dog. Once your dog accepts touch readily you can start to combine it with a down stay or sit stay. Remember that if your dog has a history of aggression related to touch then you need to seek out a Veterinarian to rule out medical issues and an experienced, positive reinforcement trainer to help you out.