I did something similar earlier this year. But it was on Reddit, so not as extreme as joining a dating website, which I have to say wouldn't have crossed my mind.
Conversations about shared hobbies (on hobby subs) led to sexual conversations, which led to me sharing some underwear photos - with several guys. Thank god, I never fully lost my senses and shared any nudes, nor my face.
I was honestly loving the attention. To have people tell me that I had an amazing body, and pay me all of these compliments was really intoxicating. Especially as I have a husband whose stock compliment has always been that I look "lovely" - never anything else and never anything more.
I realised what I was doing was wrong, and swore to delete my Reddit account and never tell DH (and would have 100% got away with it), but had such severe anxiety one day (I suffer from it), the guilt and anxiety made me tell him.
He was furious and hurt, but forgave me after a short while and we moved on. It came at a very difficult time when there was all sorts going on in our life, and I had a massive hormone surge at the same time as feeling a bit depressed about getting older. I own what I did wrong, and I couldn't have forgiven DH so easily if the situation was reversed.
We've made some changes in our marriage - one being I've made clear that I shamelessly want more exotic compliments than being told I look "lovely"!
But joining a dating website, OP. It's literally only got one purpose, what were you thinking?