Why you would meet up with someone you've never met in person for a casual sexual hookup is beyond me. Sorry, but this guy could be anything from a normal 25 year old looking to get laid to a 40 year old killer and you are meeting up with him for sex?
Far be it for me to judge you, but hopefully you are being smart about this and meeting him in a crowded environment and not simply meeting him at a hotel room, or your place or his place. If you are being cautious and he is who he purports to be, then what does it matter how he feels about your body? After all, per your post, this is just for sex. He can screw you and enjoy it regardless of your perceived imperfections. So don't get so worried about what he might think. (If he gets his kicks hooking up with older women on a regular basis, then I'm sure he has seen plenty of what modern society calls imperfections in his other conquests. In other words, your body's perceived imperfections will be nothing new to him.)
Of course, seeing that you are married, you might want to ask your husband if he thinks you should run off and screw this stranger. He might have a different opinion than mine. But if he is fine with it, then go for it. If not, why don't you put a bit of effort into fixing your marriage instead of working to help tear it apart.