Am I By Myself Or Insane?

Lately I have felt like I'm alone. Its not that I haven't been around people because that's kind of inevitable for me. I'm not sure where this feeling is coming from, its like an uneasy or unsettled feeling in the back of my mind all the time. This is not depression, I've been there, this is quite different. I am doing my best to act normal and to not let anybody know of this unnecessary, unexplainable feeling that is constantly haunting me. Any thoughts or suggestions would be extremely helpful.