I've been told I'm pretty but why do men never look at me?

I've been told I'm pretty, mostly by friends and older people from my parents friend cycle, but I guess we can't count that. I don't feel invisible only when it comes to men, I kinda go unnoticed by everyone, but that's because I'm shy, introverted and its difficult for me to talk to people especially when they show no interest in talking to me. The thing is that I've come to realize that I might not be that attractive after all. I mean I think I look okay, average, nothing crazy but I literally go unnoticed by every guy. No one will stare, look, smile, nobody will approach. I've had boyfriend's in the past but I met them all under specific circumstances, none of them really walked up to me to ask me out. When I do get noticed it's going to be some old creep who just harasses everyone at this point, barely able to walk or something. Is there a reason why or am I just ugly?

I've been told I'm pretty but why do men never look at me?
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