Why dont guys take me seriously, I've never dated or been in relationship and i'm 21?

I've never even had any guy friends, I've only had negative experiences with guys and I'm slightly scared of men the older I get and scared of having s*x with them.
I am a shy and reserved person but will open up more if I'm comfortable with someone
I wondering if its cause I'm a bigger girl and not that pretty or if my personality is boring.
Why dont guys take me seriously, I've never dated or been in relationship and i'm 21?
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