<human>: Both of them told me that they were going to date. But I guess I should provide a little back story:
I dated my ex for about 3 years and I experienced everything with her; we both shared our first sexual experiences, first kiss, first relationship. We were very close and she was the first and only girl I've ever loved. I introduced her to my best friend during our relationship and they became close; and we all hung out all the time.
Fast forward to breakup period: Ex broke up with me because of the wrongdoings on my part and wanted to remain friends with me. I still continued to hang out with ex and best friend.

last week (4 months after breakup): Ex ends our friendship because she realized that she doesn't forgive me for the wrong I've done

Tonight: Ex and my best friend tell me to meet them to talk. They tell me that they have feelings for each other and are going to date and ask me how I feel. I suppressed my frustration and rage and told them that it made me uncomfortable. They ask why and I tell them that I still have feelings for my ex. Then they seem annoyed, telling me that I have got to get over her. This is just insulting to me; I've loved this girl for more than 3 years and they expect me to just "get over it". I feel betrayed; my best friend, someone I thought I could go to during my lowest points of the breakup, dates my ex. I feel sad, angry, hurt, and betrayed. I just left shortly afterwards to cry and punch a wall in my house. I don't even know if I want to be friends anymore with him. He's witnessed my relationship with my ex and has seen how deep it was and seen how much the breakup has affected me, and he still decides to date her. I feel at my lowest fucking point in my life.

So Reddit, am I being unreasonable for feeling this way? Should I tell him how I feel? Should I end our friendship?

Can you give me the gist of the text in a nutshell?
<bot>: Feel betrayed because best friend dates my ex of 3 years, even after witnessing the relationship and my pain from the breakup. Don't know if I want to continue friendship.