miteyfrustrated

I am in need of some help. I found this forum because I was searching for some answers. I have 3 children. 2 of them (14 and 9) are outgoing and make friends really easy. My 11 yr old son, is not outgoing and is overweight. I have tried and tried to make him go outside to play, just like when I was a kid. I could not be keep inside. It was boring. I also have limited his time on the computer, TV etc... There are a few kids in the neighborhood to play with, but he just wants to stay inside. He does not want to leave my side and cries when I leave him for a few minutes to go to the store. I know he is a mama's boy, however, I have had enough of all this crying and whining from him. He acts like he is a baby and I can not take much more of it. I have went outside with him and tried to play. I have tried to help him make friends, his older brother has tried to get him to go places with him. My new marriage is in trouble because all my 11 yr old wants to do is stay in the house and be around us. What in the world can I do? Please help. Please give me something that I have not tried. I have read books on building self-esteem and alot of the parenting books. I have even asked my parents what to do. I feel like I want to yell at him, which is not the right thing to do. SO, what else? Please help