My best friend hooked up with my ex-boyfriend. Help me with how I am feeling?

I broke up with him 7 months ago. The three of us met at the same time and have been friends since then. 5 years. I would get annoyed when the three of us would hang out and the two of them would go off on a tangent about something or be dying of laughter over something I found stupid. She had even admitted when we all first met she had a little crush on him too. I am 100% sure nothing happened between them when him and I were still together though. I have even joked about the two of them dating. Then one night she asked me how I feel about him then I asked her if she ever thought about kissing him and when she says yeah we actually had sex I felt so stupid and I really hate looking stupid and was more upset about that than anything. Don’t lie to me. I was so shocked I laughed and she thought I would be angry but I hugged her and told her I love her. Now I thought I was okay with it but 2 weeks later it is still popping into my head and when she mentions they hang out I feel upset because I can’t help but wonder what they are doing. I don’t want her to feel like she can’t tell me she saw him but I totally don’t want the details. I asked if she had feelings for him or if this was a one time thing. She isn’t really sure I guess but doesn’t really see herself with him. They had been drinking and had their “needs” met I guess with a “safe” person. I feel like I would be more okay if there were real feelings but not with a friends with benefits situation. Like... if that’s all it is can you please find an other dick to hop on. She said it might happen again and she kind of wants it to and nothing can make their friendship weird. But it is weird to me so so so weird. And now I will never be able to hang out with the 2 of them. Bottom line they are two single people I have no control over who can do whatever they want with whom ever. I think I have no reason to be upset. I have no feelings for him in fact I have feelings for someone else. Why can’t I shake this?
My best friend hooked up with my ex-boyfriend. Help me with how I am feeling?
Add Opinion