Why do I want to talk things out with him should I?

My manager and I started hooking up 6 months ago and I agreed to do it with him if he promised to not hook up with anyone else at my job. Throughout the months I could tell him and I started growing feelings for each other and becoming more intimate but he told me doesn't want a relationship because he just got out of a 5 year relationship. Anyways I recently found out he did hook up with one of my coworkers who I had a suspicion on and kept asking him if he hooked up w her in the past and he kept saying no and that he would never do that to me bc he knows how upset I would be. When I found out he hooked up with her before she got into a relationship, I was shattered and so heartbroken. I felt betrayed and angry bc he lied to me for so many months and would talk all this shit about her just for my gut feeling to end up being right. So when I found out I told him to never ever talk to me again and stay away from I want nothing to do with him and unfollowed him on instagram. It has been a month since we have spoken to each other but I still see him once a week at work. Now at work he doesn't even make eye contact with me or speak to me but I know he wishes he could. Every time I see him I can't help but be so angry again and wanting to be mean to him by how hurt I am. So yesterday at work I was being rude to him & when I left one of my friends at work told me how he was telling someone else how mean I was and lashed out at him for nothing. So then I got pissed and impulsively texted him that I would tell hr to get him fired if he continues talking about me. He unfollowed me on instagram after that and now I want to try to talk things with him. What should I do?

Why do I want to talk things out with him should I?
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