I feel about the same. For a long time I had 2 closest friends from University, but then our lives went into different directions. One decided to be actress and now is hanging out with her new friends, I'm not anymore interesting for her, so we totally lost each other.
With the other we also grew apart, we used to have great time together, then we went to work, she found new friends, our lifestyles changed a lot, so we meet quite often, but there is this uncomfortable silence all the time, you know. We have less and less common topics for conversation.
Certainly I meet some new people at work etc, but they are very different from me and I can only, let's say, go to drink coffee with them, or attend some concert, but we are not close at all. When I changed work I immediatly stopped seeing all my "friends" from there, so you see my point.
I never was good at making close friends (and just friends, I'm too shy at times), and I feel it becomes harder when I grow older. I desperately need new friends, people with the same intersts as me, but I don't know how to meet them.
I'm afraid to be absolutely alone in the future, if that will go on like that.