I wonder this myself OP. Someone recently look a photo of me that was absolutely horrific and shattered the mental and mirror images I have of myself. To be fair I was working in a river at the time so not exactly the most conducive circumstances to a good photo, but it really upset me and since then I've been spiralling about my appearance. I wanted to cut off my face!
I've always thought I looked really odd, deformed even. But in this pic not only did I think I looked odd, I looked old and odd.
I had a fair bit of attention in my 20s, even had men come up to me and ask for my number (I ended up in a relationship with one, he was really sweet, not a pick up artist) and was told I was beautiful, but I never truly believed that they believed it. I just can't see it. I think I'm hideous. I'm in my mid 30s now and avoid men so I've no idea if I've still 'got it' or not.
There isn't any one thing 'wrong' I feel I could change, it's the general proportions of my face. I have a deep bite which gives me a weak chin so I've been considering orthodontic treatment to fix it. Because it causes other issues I've been offered it on the NHS, but they said there's no guarantee it will actually fully correct the bite. I wouldn't do botox or anything like that as I don't think it really improves anyone's appearance, to my eyes it just makes them look like they've had botox.
I wonder if I have body dysmorphia as I look at everyone else and think they look normal, it's just me who looks like a freak. If I see a photo of someone with a facial deformity or injury I still find myself wishing I looked like them instead of me! The voice in my head tells me that it's not BD, though, I'm just really bloody ugly.
I hate that I'm so vain as to give any of this a second thought. Why does it matter? Who cares?
I think there's a very strong chance there's nothing wrong with your appearance but instead, your brain is zooming in on perceived flaws that have been reinforced in your mind for years, that nobody else notices. Deep, deep down I know there's probably nothing wrong with mine either. Perhaps look into therapy to try to work on this. I intend to myself once I finish EMDR.