Guy's Behavior

What does it mean if a guy laughs when you hug him and lets go quickly?

He's been one of my closest and best friends for a decade but we don't usually hug each other, there's just an awkwardness or unspoken thing that we just don't get physically close to each other. Lately, we've only hugged a couple of times but he does this kind of nervous laugh when we hug and lets go of me really quickly. It's noticeably different to his hugs with other female friends which are much longer and more natural. I'm trying to work out if this means he might have a crush on me or if he just has an aversion to being physically close to me?
What does it mean if a guy laughs when you hug him and lets go quickly?
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