Sad and Broken

In 2015 i had sex with someone at work 1month later i met the most amazing man i my life (my current boyfriend) once i told him what happened between me and the guy he told me to stop talking to him. (i never talked to the guy outside of work EVER. I didnt like him like that nor did i have feelings. And when at work we talked in groups or hi-bye type things . never deep convos. it was honestly a one time regretful thing that happened.) however my boyfriend (before he was my boyfriend)expressed to me that we could be together or even "talk like that" because he was moving but he still didnt want me talking to that guy AT ALL. A couple months later he decided that he would stay and i continued to talk (only at work) to the guy for about a month after we were together. A year and some months after being with my boyfriend he breaks up with me saying that he just cant take the pain of knowing that i still talked to that guy after he told me not to. Has he taken this to far or is he right for breaking up with me? (PLEASE BE HONEST AND BLUNT ) thanks