Need help to stop feeling jealous/upset

In the past, my ex left me for his co-worker. My current partner of 4 years, who I live with, and work in the same building, has a new female co-worker. They work closely together and share an office. He was on annual leave and she asked me how he was and brought up private family matters - asking how they were. My partner has always been a private person so this surprised me. I asked him about it, and said I thought he didn t share private details with co-workers and he said usually, but sometimes he does. I absolutely know, he would never cheat and it's normal to share details of your life with co-workers - I do it myself....can anyone offer advice on how I cope with this? Talking to my partner annoys him cause he makes it about trust and the one time I brought her up I asked him to be friendly, not familiar....I just need help calming my farm cause of my past and I'm completely insecure.