My partner and I have been together for 18 years- we are both 36 years old.
Our entire relationship he made is very clear that he did not believe that men and women could be friends. As a result he made my life extremely difficult when it came to socialising as a mixed group of colleagues as men would be present. To the point, that I couldn't do it as it wasn't worth the days of arguments afterwards. I never felt the same way and used to encourage him to socialise with his colleagues when they were going out as a group.
However, I recently saw that he and a female colleague were exchanging almost daily messages on Instagram. He didn't know that I had seen these messages and it didn't bother me, but I became suspicious when I saw that he had deleted them. I confronted him about why he deleted them and he said there weren't any messages. When he couldn't deny it anymore (because I referenced one of the messages), he eventually admitted it. I later found out just after this that he had been going for drinks after work with this same female colleague alone on multiple occasions. He says that the dynamic in his office is a 'sociable drinks after work' environment. However, I feel like it's crossing a boundary to go alone for drinks with a female colleague and especially after deleting Instagram messages (they seemed innocent but he also lied about them). He thinks that I am not understanding his work dynamic and that's why I find it inappropriate. And if I understood then I would think it was perfectly fine (he has worked in this industry for 12 years so I'm not unfamiliar to it).
Am I wrong for feeling uncomfortable with this? I personally feel like it's crossing a boundary to go for drinks alone on multiple occasions. I also feel like I struggle to understand how he doesn't see it in the same way given his jealousy issues. Any advice is appreciated