I have the same problem Jeff. I'm relatively introverted and have a hard time making friends. Only difference is that I never really had any close ones while I was on the inside either, so there's no longing to go back for that reason. But I do understand how you feel.
Oftentimes I feel very alone and isolated from the world. I'm a little younger than you, but even at my age, it's difficult to find deep meaningful friendships. I think that others have given you good suggestions, such as volunteering or joining clubs. Because of our introversion, making friends is difficult anyway, but I think the first step is just getting out there where the people are and finding those with common interests.
I hope that these feelings soon pass for you. I wish you well in your recovery.