Friend + ex + me = weird?? Or is it just me?

Idk if this is weird or just me.

I dated this guy at work for like a month, about three dates and we saw each other at work most of the time. I ended up break it off with him as I wasn’t looking for a relationship and therefore couldn’t form the same emotional bond that he had for me. We didn’t do anything but kiss as we are both virgins and clearly a bit sketchy about starting something.

Fast forward like 2 months or so, everything is back to normal but the thing is that my (girl) bestie is now his bestie which I am fine with as we are all close. But I heard they have been talking quite sexually over messages. I don’t believe he likes her romantically, but I think she might like him.

The other day we had some drinks and he was there over call. The conversation got quite sexual about all three of us, by asking and revealing sexual fantasies etc.

from this I think he is interested in having sex with both of us. But is that weird?

I think he still has some feelings for me, but idk how if he is dtf my BFF.

Someone needs to be honest with me and tell me if it is weird.

I want to have sex with him, but it’s weird if my bestie does or wants to as well. That’s just how I feel. I also don’t want to sleep with him in case he sees it as leading him on, but she doesn’t have that possible consequence as I don’t see them dating soon… but what if they do? Is that weird?

Am I jealous? Or does this happen to others? Or will nothing happen and being sexual is just what a bunch of horny virgins do?

I’m so confused