<human>: She and I had on and off flings since we met about 6 years ago but remained extremely close friends all throughout. She wanted to date from the start, but I didn't want to for various reasons. 

When we finally did start dating, it became clear that she held resentment for me not staying exclusive with her in the beginning. I was not innocent here. But I sometimes think that it wasn't as terrible on my part as she made me feel about it. It didn't affect our relationship usually, but it would occasionally bubble up. 

She sort of cheated on me about a year ago. We decided to do an open relationship while she studied abroad. The day before she left she fucked a guy I knew that she knew made me jealous. 

We stayed together for a long time afterwards, but there were trust issues. I saw that she had been talking about our relationship with our mutual friend online. She said she was just comforting him after his break up. 

It wasn't very surprising when she dumped me. 

I was upset, then I was moving on. Hardly thinking about her. Pursuing other girls. Doing me. 

Then I was tooling around on FB today and was looking at that friend's wall. There was a picture of him that showed he was at her apartment two days after the break up and possibly for the weekend prior. 

They live about an hour and a half apart by train. It wasn't like he just popped over real quick. And I noticed that they were suddenly liking each other's posts a lot. I think that they are hooking up. Or that something's up at the very least. 

I felt like I was moving on. Then I happened upon that. Now I don't know what to do. I am still friends with all the guys in that house. That would be weird as hell. I have plans to hang out with them this weekend. Can't handle this.

Can you condense the text into three sentences or less?
<bot>: recent ex might be hooking up with mutual friend and exhousemate. Can't stop thinking about it. What do I do?