Most experts in child development and raising do not agree with monicak4evr. What she is suggesting is spanking. It, spanking, has been proven that it does not work. Read the book SOS for Parents and use the suggestions in that book. Do not spank your child. It will make things worse.
I know some count this as "abuse" But ireally dont think so. GIve him a smack on the hand. or a slap on the butt. Not too hard, since he's young. When i was little that always taught me. If my mother just sent me to the corner. Heck. I'd just draw on the walls. Or.. you can take things away from him.
Your son may well display hyperactivity along with a difficult temperament. You would be wise to arrange an evaluation with a pediatric behavioral health clinician. At the same time, the clinician can guide you about managing the behavior. If you notice that others are able to manage the behavior better than you can, it may well be that you have developed some bad habits in your management. So, while there may be something in the parent/child interaction that invites concern, there is also the need to figure out what is happening with your son in terms of his emotional or neurointegrative functioning.
First, you need a new pediatrician. No doctor should talk like that to a mother.
Now, if all kids were like your son, the world would be empty. Motherhood and parenting in general should be a fun and loving experience assuming you have your normal / average child. That is why parents usually want more kids. Assuming you are an average mother (not spanking, not yelling or abusing your kid), the issue is not you and it is probably your son. You need to get him evaluated by a child development specialist or psychologist, figure out if something is really wrong and take care of it. Do not put yourself down. He probably has ADHD or he might just be spirited. In general, three year old boys are not easy. I have two kids. One was easy and the other was NOT. If I knew that my third child was like the easy one, I would have a third child. Since the odds did not favor me, I did not have a third. So, get a new pediatrician that can refer you to a good child development doctor and speech therapist and start helping your son be the best that he can be. As they get older, things get easier. My hard to raise child is now 9 years old and much easier (and a joy) versus what he was at the age of 3. Do not give up. Take good care of yourself and your family.