Very Fustrated!!!HELP!!!

My son is 7yrs old and he have been over weight since he was 1yr old we is currently 140lbs. I have tried numerous attempts with diets and exercise but he always complains that he is tired and that his feet hurt. Now he starts to tell me that the kids at school have start calling him fat. I have been overweight most of my life but I don't want him to have to go through the same stuff I had to go through when I was in school. Does anyone have any suggestion of were I need to start. Even though I have made several attempts with exercise and diets I didn't want to over do it and something bad happen to him. Can someone please give me some advice.

I'm sorry I don't have much advice to give, only to tell you that I completely understand your frustrations.........my son just turned 11 and weighed 203lbs at his checkup.
The dr goes on to basically tell me that I was lying about him drinking empty calories and eating junk all the time.  He told me to make him do something physical (no tv, video games, computer for hours) for the majority of the time he his at home.  He should earn "couch potato" time only after physical activity.  He then said to NEVER allow him to drink anything with calories, cut back on junk, bread, pasta, fats, sugars, etc.
It'll all work itself out he claimed.
I put him on a strict diet for the last month and he lost a grand total of 3lbs and that's all.  This is with 6-9 hrs a week of heavy physical exercise at football practice on top of the 30+ min per day of treadmill and elliptical equip at home.   I don't know what to do!
He was a normal weight child until kindergarden when he got his tonsils out at the beginning of the school year and had gained 25lbs by the time school ended in May.  He has continously put weight on since that time regardless of his diet.  He's just steadily gotten larger and larger and I'm at a loss for what to do.
My husband and I both have had the DS wls and I do not want to see my son have to go through surgery to get his weight off.

My suggestion is to meet with his pediatrician and have them give you a specific diet to follow and see if that helps.  I personally am thinking of going with Nutri System for my son if this new diet doesn't start working in the next month or so.  We go back to see his ped. in 2 more months and I'm going to take a detailed food diary and exercise log with me to show we have been trying.