Please Please Please try this before having him tested for ADD/ADHD, it is my opinion that way too many children are being treated for this with highly addictive medicines that have several side effects. My daughter was very very stubborn when she was young, and really still is, however, we have learned how to deal with it.
Give him choices...example: He asks for a drink, you say:
Would you like the green cup or the blue one?
Would you like a lid or a straw?
Would you like milk or juice?
Would you like to drink it in the kitchen or the dining room?
Would you like to sit at the table or stand?
The key is trying to give him as many choices as possible, just remember to always give him 2 choices that you are happy with either choice. Usually stubborn children is all about control, they need to feel like they are in control and this way they feel control because they get to decide and decisions are not just made for them. If at first he refuses to choose one of the choices you have given, just choose one for him and he will quickly learn that he must choose. Just be consistent and stick with your decision, even if he throws a fit.
This method will also work with disipline....example: He does something that is unacceptable. Give him a choice of time out in his room or in the chair (or something similar). Just remember to give him 2 choices that you are happy with whatever he chooses.
This worked with my daughter, who is deaf and communication was a struggle too. She is now 16 and even though she is still stubborn, she has much more respect for us as parents because we allow her some control in her life.
Hope this works as well for you as it did for me. If you have any questions, or need some support, just give me a post and I'll try to respond right away.