I don’t think it was necessarily the sexual history itself that made him this upset, but the combination of hearing about it from a coworker, and having no idea you had this history. Put yourself in his shoes, how would you feel? The fact that you have been together this long and having discussed each other’s pasts even a little bit is odd to me, and I feel like you may have been purposely avoiding it. I mean, he’s asked you to do anal before, yet didn’t know you had done it in the past? It would have been easy to say “I tried it a long time ago and didn’t like it.” But you didn’t. Not that it’s anyone’s right to know every detail of their SO’s past sex life, but to not know any of this at all seems like a lie by omission. All I can say is that he needs some space to cool off, and you say you are sorry he had to hear about your past from someone other than you