You are in good company my friend. I'm 39, married, 2 kids. Growing up I always had friends. I made friends quickly in college and when I joined the Army I made fast friends there too. Then, when I got out of the Army and moved to Connecticut with my wife, got a corporate job, started a family, etc... I met "work friends" but nobody I would really consider my friend outside of work. Been working in the corporate world for 11+ years at this point.
After leaving home, college, the Army, etc... my friends kind of drifted away as our lives went in different directions. This is something that has taken me literally years to realize/get over, and it's still hard to swallow sometimes. For example, our group of friends growing up were super close and I feel that it's so sad that everyone drifted away from each other. I saw everyone at a wedding a few years ago and I went home afterward so disappointed/hurt because it seemed like the connection was gone and nobody but me was interested in keeping the friendship alive. I don't "do" Facebook, and if you're not on Facebook you don't exist, evidently. Out of sight...out of mind.
Really my wife is my best friend, but it would be nice to expand that to include male friends to do man things (go fishing, hiking, eat buffalo wings, etc...). She feels the same way about herself, finds herself hanging on to the hopes that her childhood friend will some day turn back into a real friend again but no dice. The topic comes up every few weeks and she usually says something like 1)"well I encouraged you to join that indoor soccer team back when you were in grad school" (12 years ago), or 2) Maybe if we joined a church we'll meet friends there. I somehow have my doubts.
My wife and I are not terribly extroverted and we thrive best in small social groups. I wouldn't say that we are handicapped by introversion, ie can't talk to people. I suspect everyone else is either 1) well established and isn't interested in making new friends or 2) people think we are complete assholes and don't want anything to do with us. God knows!
Anyway, hang in there...I hope you find some direction on here... if you come across any good ideas will you let me know?