Why am I always overlooked by guys?

Everytime I go out I'm always overlooked by guys no matter who I'm with they always get chatted up or attention and I never do. I 'm not very confident with guys and have never had guy friends but I feel like everytime I put myself out there I'm rejected so what's the point. I've had so many situations when guys have been nasty or negative to me and it hasn't been provoked in any way. I've been trying to accept maybe the only way I can move forward is to accept that guys just aren't going to be a part of my future. But being balatantly overlooked constantly is destroying my self esteem and I don't why it's always that way or what to do about it.
Why am I always overlooked by guys?
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