Am I overreacting or should I private message a girl I suspect my boyfriend is cheating on me with

Hey is it a good idea to dm a girl I think my boyfriend was talking to, they don’t follow Each other anymore but I keep thinking about it it’s like I have no actual proofs I can bring up to him so I’ve been suffering quietly. Should I just forget it, or send a message, I think he does this with other girls too but this one girl looks like a girl I could be friend with so this is why I would be friend with, this is why I chose her. I’m really desperate how would I even approach it, any help would be appreciated