as a result I'm clearly never going to have amazing sex ever again with an attractive man!
Girl, you are so wrong I don't even know how to tell you.
Men are realistic. They might wank over the thought of banging a size 8 model with fake tits, but the ones that aren't shallow as fuck accept that women come in all shapes and sizes, and being in bed with a willing woman is as much turn on as they need.
He already knows your general body shape and your age and parental status, right? Unless he's a teenager, he's going to realise that your body has done amazing and wonderful things and that as a result your body has the marks of experience.
If you're anxious about the first time, there are many flattering lingerie options - basques to nip in your waist and accentuate your boobs, babydolls to just loosely cover everything, deep suspender belts to contain anything wobbly...
I am a size 16, massive arse, thighs and boobs, I have bingo wings which I hate, surgery scarring and a big pouch of saggy stomach skin. I fuck a LOT of guys and not one of them has ever screamed and run for the hills when I've took my clothes off :)
Confidence is hard to find when we're constantly bombarded by mass media telling us how we "ought" to look. So stop consuming mass media as a good first step. Then... fake it til you make it. Confidence at size 16 is waaaaaay sexier than a perfect figure hiding under the duvet saying "put out the light!"