Help!!!

So I was cooking breakfast when I walked to the couch to get my phone. As I was walking behind My bf was talking about getting his haircut and pulled out his phone well as I walked by he turned it on and I just looked down. I saw a text between his former coworker where she had sent him kissy faces. I ask him why he lets her do that and he gets upset with me. Saying I’m always looking at his phone blah blah. I said you wouldn’t like it if my guy friends did that. He said you don’t even know why she did it. It’s a joke. I told him I didn’t care she’s done stuff like that before and I’ve expressed to him it makes me uncomfortable. She has told him before that she has feelings for him. I am completely unsure of what to do. He’s not a morning person so I know talking to him now isn’t going to help because he’s only going to get meaner. I don’t know if I should believe him or not. A lot of me doesnt because of me having to repeatedly say something. But with everything I know about her I don’t feel he’s attracted to her. Either way it’s not okay I feel. I’m just not sure what to do. 😔