P.-
I've found that if you don't listen to your gut and your child, you'll never get to the bottom of what's wrong.
A little Tylenol never hurt anyone. If you think it's cramps, then it's probably growing pains, and he may end up being a very tall boy. Trust yourself.
If it continues, and your doctor is still resistant to the idea, then I would change doctors. You have to be your child's advocate, and sometimes that means bringing out the claws.
I don't know what part of town you are in, but if you decide to change doctors, my daughter's pediatrician is wonderful, and he'll listen to you. I wish that we'd had him from the beginning.
Let me know if you need anything,
A. Boyd