Hi T.,
My son was also born at 10 pounds. I have found no problems with him. He is at the 95%. Right now he is 28 months old and weights probably 40 pounds and is 40 inches tall. My husband is 6'3 and I am 5'9 so we are both tall people. Wait until your son is rolling over, crawling and walking and he will thin out. When he was born he had two herinas and his testicals did not drop. With the herinas, it was very painful for him to have tummy time. Which meant he spent a lof of time on his back. But he had double herina surgery at 4months and has his testicals tacked down and at 5 months he had to wear a helment because of not being able to have tummy time. It was a long first 8 months. But now, if you look at him, you would never know unless I said something. Don't worry, your son will be just fine. Everywhere I go, people tell me how cute he is with the cheeks you can just pinch (although, my son hates it).
Enjoy your son! They grow up WAY to fast!!!
Lisa