A Slip of the Tongue Turned Into Something More

I've been married for over twenty years now. We're still together and happy as a couple, but I haven't felt sexually attracted to my husband in nearly ten years. It's not because he's not good enough or anything like that, it just happened naturally with time. Sometimes we cuddle or kiss, nothing more. We've accepted this part of our lives and both agree sex isn't necessary for a healthy marriage. Anyway, recently I joined an online dating site to explore my feelings beyond what I have with my husband. It's not like I want to leave him; just wanted to understand myself better in case one day it changes between us. Anyway, through the app, I met this older gentleman who is also married but looking for some casual hookups on the side. We talked a lot online about our lives and fantasies. He was very charming and sweet, making me feel appreciated. Then out of nowhere, we had a video chat and he asked if I wanted to see him touch himself while talking to me. At first I said no way, felt like it would be too weird. But then as the conversation went on, I found myself agreeing just to satisfy his curiosity. And before I knew it, I was getting off on seeing this married man pleasure himself for me. I know what you're thinking, how could I do that? How can I enjoy watching another woman's husband when my own marriage is lacking in that department but still good otherwise? It just feels so wrong to be honest. But also kinda liberating too since it allowed me a rare escape from reality, even if only for an hour. Afterward we ended the chat and haven't spoken much since. I'm afraid of ever getting back in touch with him again after that encounter, but can't get it out of my mind either. Guess I'll have to figure this one out on my own now.