Husband messaged by 3yr ex :((

I accidentally saw a messge on my husband of 1 1/2 yr on his phone and it was from his ex of three years.  I did read it it was nothing bad just informing about life events. But I can't stop being so jelous and betrayed. If it was nothing bad should I bring it up or wait for him to mention it. I have a feeling he won't. I need someone to tell me before I go mad with jealousy. I'm very sad about this :(