Split up with my fiancé over his female coworker.

Hi everyone! I am the 30F and my fiancé is 32M. We’ve been together for 2 years and are scheduled to get married in a couple months. Over the past 2 years I’ve always sensed uncomfortable about his friendship with a particular female coworker (they’ve worked together with regard to 5 years). She’s our own age and married. They might go hiking together one-on-one. Have dinner together and so forth Her husband works night time shift. If she’s having a bad day he’ll get her a small gift. He does lots of these little gestures for her to show her that he cares. When the lady was at the hospital having a baby, he worried about the kind of food she was eating plus wanted to bring her food when I told her that it was the girl husband’s job to take care of the girl. He got mad from me for saying that. I have seen him text her stuff before like “you worry me” and the girl saying back that her husband wouldn’t be too happy hearing that followed up with a jk. Sigh. Recently I found out that he lied about having dinner along with her to which I responded it needs to be me or even her. I can’t think about having kids with this man and arguing about additional women pregnant. He informed me that they don’t even talk as often anymore and he doesn’t need to cut her off but I feel like it is a respect thing. He or she doesn’t respect me or maybe the relationship. I feel like he’s emotionally cheating and this is a classic example of having a work wife. Sigh. Advice is usually appreciated.