I'm dating myself here, but do you know the song "Alone again, naturally"? That's often how I feel. I recently learned that some of my "friends" are intimidated when I'm around. So, now, I wonder if they want me around. Or, even worse, if they are friends. It is very hard when you unconsciously "know" more than the people you are around and never mean to sound like a "know-it-all" and then someone tells you that's how people perceive you. It then makes all social interactions hard because I'm constantly second-guessing what I'm about to say and then sometimes miss the opportunity in the conversation completetly because I'm concerned that what I want to say will be the wrong thing to say. Then, I'm told I'm "standoffish" and "aloof" because I don't participate in conversations.
Is this the kind of thing you mean? I, too, feel the intensity and find it hard to fit in anywhere.
I wouldn't blow off the ADD diagnosis, though, before you look into it fully (which maybe you have). It could be worth considering.
