Husbands female work friends

I’m really having a hard time being comfortable with my husband having female work friends. One female friend in particular that stood out because he talks differently to her, like overly nice. Before this, We’ve had issues in the past with 2 different female co workers. One co worker he used to call her his “work wifey” and i found a diary that they would both write on and its basically just them flirting with each other back and forth. The other co worker, i found some flirty text and they would literally flirt right in front of me, she would take selfies of the two of them at work and always arranges play dates with our kids and hers. She ended up being separated with her husband and started dating a co worker soon after. At this point though my husband had made an effort to stay away from her. But now that thats over im seeing similarities with how he speaks to this new “friend”. I dont know what to do any more. Ive communicated to him that im uncomfortable with where this friendship is heading and he thinks im just over reacting and tells me that everything is a red flag to me. Also he thinks that ive ruined those past “friendships”. And blames it all on me for being insecure. I wasnt before but based on what he has done,how can i not be? Any advice?