Should I message the girl who has been commenting on my boyfriends instagram?re

I’ve been with my partner for 2.5 years and I’ve been noticing a woman commenting on his posts on ig. I asked him about her and he said he didn’t know her and she was just some Instagram garden tool that he follows. I just thought it was suspicious because she lives in our same city and he’s been dating only me since he moved here 2.5 years ago but I let it go. I was at his house tonight and he was talking about how he feels about marriage and I was named nowhere in that picture. I didn’t say anything because his son was in the room with us. So tonight I come home and the woman posted a comment on his IG that definitely indicates that they talk outside of ig. I’m 43 and feel so stupid and insecure and that I’m too old for this bs but I want to contact her so bad and ask what the nature of their relationship is. I know I shouldn’t but I really want to because I feel like I’ve wasted so much time with him and don’t want to waste anymore. What do you guys think? Should I contact her?