Serenity, if you weren't able to spell and punctuate sentences, I'd think you were the arsewit who caused me to flounce from another forum.....
But hey, moving on.....OP- what about swimming lessons for your son? I took dd for lessons this summer, and ended up sitting on the poolside bench with the other mums and you're kind of forced into a bit of social interaction with such close thigh-touching proximity...it doesn't have to form long lasting relationships, but it's a start, and I did use to come away thinking what a nice half hour chat we'd had....
I'm an only child, my dad is an only child, my daughter is an only child. She is the polar opposite of me, sociable, loves nothing more than to be in a group of friends. (I hate it. Am people-phobe, which is why I like t'net so much, I don't have to see you all) Just to show you that your son's personality is diddley squat to do with either being your son, or being an only child. He is who he is. Is he happy? Does he show distress at not having many close friends, belonging to groups etc? Or is he doing OK?
I would be wary about forcing friendships onto him. I remember my Mum, when I was little, "making" me go and play on the street with the other kids. I used to sneak back in the front door, up the stairs, grab a book and sit under the front room window until she found me and chucked me out again. She still thinks I'm weird. Maybe I am. But I was never unhappy on my own.
You obviously are, though. It seems from reading your posts that it's more a problem for you, this loneliness thing....Just one step at a time, go to the library, the park, try and start up a conversation with some other mother (or even just a normal human being ) Small steps etc.