<human>: Provide a brief overview of the text.

We had been dating for 20 months, and suddenly coming back from summer to college she didn't "feel the same spark".  So I let her go and did my best to move on. 

One of my best friends that I go to for advice has been acting weird about my breakup. I suspected they had sex because I know him and he is out for any girl he can find, and she was vulnerable. 

I confronted her one night after she flirted with me all night drunk, and told her that I wasn't okay with them together and that would hurt me. 

It had already happened at the time and then they continued to meet up. She told me all of this last night when she spent the night but nothing happened. 

I asked him point blank last night if they fucked and he said no. He lied to me, and tried to make it sound like he was trying to just be a good friend to me and her.  

I know she is sorry, she cried a lot last night but they knew what they did. I understand why both of them did what they did but I need advice on what I should do next. 

How do I not hit him next time I see him? What do I do, who should I be more mad at?
<bot>: One of my 2 best friends actively went after my ex and slept with her. Then they both lied, until I finally got the truth. Who should I be more mad at?