I went several years without post divorce, then "discovered" Fwb options.
I didn't and still don't really want a full on relationship.
Currently about a year celibate due to health issues.
But stocked up from lovehoney thanks to a recent mn discount.
It won't always be like this, but I remember the feeling and fear that it would be.
The insecurity of worrying about my first time with a new person since having dd and the changes to my body that caused.
Somebody lovely said to me not to worry, that they'd have their own hang ups to worry about (weight gain of their own, balding, possible erectile dysfunction, height etc) and by the time we were at the point of having sex they'd already have a reasonable idea of what to expect and were clearly happy with that - else they wouldn't be there.
As it happened my first time post divorce I absolutely wasn't prepared, it was a drunken ons following impromptu drinks after work I hadn't even shaved! He didn't care, good time had by all, tad awkward at work for a few days (we weren't otherwise suited nor did either of us want a relationship) but that soon passed.
It was a bit like losing virginity - great angst beforehand, afterwards wondering why you bothered with the angst 
You'll be fine.
Go at your own pace, consider old but there's also more - ahem - direct sites you can use if you'd prefer a more...pragmatic arrangement.
I actually prefer them as you can be more upfront about expectations - no pretence at virtuously only having sex within a serious relationship, honest discussion about likes and dislikes, including body types etc
But also be safe and let a trusted friend know what you're doing and have first time meeting somewhere public etc