Jude - i know that feeling exactly. and i remember others here expressing it similarly.
i always feel like i don't belong. like i am different. like there is a big sign on my back that identifies me as a phony who is masquerading as a real guy. (notice i didn't even have the nerve to say "man.") like the others are just tolerating me and can see through me and will be glad when i leave. like i am an outcast who has deceptively infiltrated the ranks of the normals and is likely to be exposed at any moment. like i am outside myself observing how inept and what a big loser i am...
face it - we ARE different. we have experienced things that set us apart. we see things from a different perspective - and have deeper insights to some issues - and no common ground with normal guys in other areas. nobody ever taught us how to be one of the gang.
and sometimes i am glad that i am not as shallow and mindless and simplistic and as much of an instinctive animal as the way i see them. and other times i long to be just that - with no reason to have to even consider anything but the trivial stuff that occupies them.
in short - NO - you are not alone.
"That you are here - that life exists, and identity; that the powerful play goes on and you may contribute a verse. . . What will your verse be?" Robin Williams as John Keating in "Dead Poets Society"