I’ve always felt like this too, although maybe my feeling is and was more of feeling ‘flawed’ than just different. Looking back, I think it stemmed from an abusive childhood, and being bullied for having an ‘odd’ family (both parents had MH problems), and then for being fat (I started to comfort eat).
Along the very bumpy road of my life, I’ve found quite a few of ‘my people’ along the way. They tend to be people who also come from ‘unconventional’ or abusive backgrounds. So now it’s a little less lonely, but it’s still lonely all the same.
I think one aspect of me feeling ‘different’ were the result of emotional neglect as a child - it’s like there were many aspects of my personality that never got the chance to develop, leaving me very unsure of who I actually am or was if that makes sense? In hindsight, I feel like most people around me were much more self aware and aware of who they are way before I was.
Obviously I can’t speak for everyone, but I suspect that feeling of being ‘different’ is a symptom of some form of dysfunction in our formative years, whether from attachment issues, abuse, bullying or trauma.
What I have found though is that the older I get, the less I care about feeling or being different, so I suppose that’s good.