Not sure what sex club you're going to, but most sex clubs I've ever been in most people will take their shirt off. Have a jock etc. Generally, if you're kinda fully dressed, it looks like perhaps you just got there or you're leaving. I love the word skinny fat. That's a good one I would have to kinda say I'm in the same park. It used to always bother me.And I too was ashamed of the way I looked.
But the real key here is you only live one life, accept your body.
There's always going to be somebody that looks hotter, better, more muscled, more toned or whatever.
Ditch the shirt, put on a shorter pair of shorts maybe a harness. Get yourself comfortable with less. Nobody's honestly gonna care what you're wearing but less it better. And there's a type for each and every person embrace it, go for it, and twenty years from now you'll be glad you did.
take the direct approach, ask people if they wanna fuck twenty people might say no, but the twenty first one I might say yes, you won't know unless you ask. In sales, there's an expression called ABC, always be closing.... to complete the deal in the baths clubs it's ABC but it ass butt cock. If ya ask enough cock to fuck you in the ass, your butt's gonna love it..
have fun.