His EX Msgd him

My boyfriend and I were lying in bed a few nights ago when his phone dinged because someone had messaged him on Facebook. He said it was one of his guy friends, something just seemed fishy because he didn't open it. I asked him why he didn't want to open it and he said if I open it, it'll show that I read it and he said he just didn't want to open it. I made a little bit of a stink over it and he went back into the message and he's like "oh, it's my ex that messaged me." I read the message and she said something along the lines of "I found an old picture of us and it brought back a lot of memories. It looks like you are happy, I'm glad you found a good one." Idk why but I started having an anxiety attack and started shaking because it upset me so much, I thought he was lying about getting the message because he wanted to respond to it and didn't want me to know she messaged him. Now I'm sitting here wondering if he still has feelings for her. I did end up messaging her from my phone just stating, "He says he's happy, thanks for asking." He didn't care that I messaged her and said he thought it was cute that I messaged her defending him and he got super horny.

I asked him the next day if he responded, he said no and he deleted the message that she sent him.

Do you think I have anything to be concerned about? I'm probably overthinking this...😞

He also did add with the holidays coming up she probably is feeling lonely and that he thought about her when the holidays would come around when he was single. They dated almost ten years ago.

From what people are responding I was hoping it's nothing I need to be concerned about. It's hard to trust men, my last two boyfriends cheated on me, but I think I found a keeper ❤️. Thanks for the input so far, makes me feel relieved ❤️❤️