How can I get my boyfriend to let me wear "short" shorts and skirts?

And by "short" I mean above my knees. It's so unnecessary. Other guys will look at me anyway and we shouldn't care what they think. And I hate long skirts, I myself am too short for them. I hate looking in the mirror and feeling like a stupid kid or a frumpy old lady. I just want to feel cute. He's not the only person in the relationship who's opinion matters.
How can I get my boyfriend to let me wear "short" shorts and skirts?
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