Best friend’s husband flirting

I posted this in the wrong room so hopefully this one is ok.

This is a seriously messed up situation and I wish I could say I am completely innocent, but I’m not.

My best friend and her husband decided that they would be in an open relationship because they had both cheated with close friends and they wanted to save their marriage by being ok with it.

Her husband is incredibly attractive and he recently started flirting with me, and I played along. Imagine being one of the rejects in school, and suddenly the most popular/hansome guy starts flirting with you. That’s how it made me feel. And like, I Longbottomed after high school, so I think he’s actually interested and not just messing with me. I didn’t initiate the flirting, but I didn’t say anything to stop it and I rolled with it trying to turn it into something funny and didn’t give any signs that I was against it, even possibly the opposite.

It never got any further and I don’t want it too. I know so many reasons why this is bad, and I want it to stop, but I don’t know how to make it stop without hurting anyone’s feelings or relationships.

So here are all the reasons why this is twisted AF.

-He is married to my best friend and they have kids

-I have a boyfriend in a closed relationship and we also have kids.

-His wife is the godmother of my child

-His dad is dating my mom, so not blood related, but still weird.

-He and his wife are responsible for my children if something happens so I do want them to mend their couple.

I feel terrible about not shutting him down the first time, it just made me feel so confident about myself....

The flirting has to stop. How do I tell him?

Also, this only occurred on two evenings, one during which I wasn’t certain whether he was flirting or just friendly and the second time where I played along but regretted immediately and left early.

What do I do? I feel terrible and I want to make things right. I don’t want to tell my bestfriend because I think it would end their relationship and he is a great guy and great father to their children. It was « just » flirting, but it feels like a huge deal to me. Am I a cheater because of this? Should I tell my boyfriend? I feel like I can’t tell anyone because we are just all so tangled up that everything will crash for my best friend if it comes out.

Update:

I told him that we crossed a line and I’d rather we kept it just friendly and we’re cool now.

I told my boyfriend about it without saying who it was and he was ok with what happened and how I handled it.

I also ended up telling my friend about it and she was 100% cool with it. They apparently both have slept with friends of each other and are ok with that 🤷🏻‍♀️

She even told me about a conversation they had during which he told her that if he could get a free pass and sleep with anyone he wanted, it would be me 😳. Now, I’m not about to cheat on my boyfriend and he (my boyfriend) is not interested in an open relationship, but damn, I almost wish he were.

I am going to hell 😫