My friend asked me to help me with some advice. She's having problems with her boyfriend:

I have been in a relationship with a guy for 1.5 years, but he doesn’t want to talk about his past relationships. I found a message from his ex five months into our relationship, saying she was sorry about the argument they had, and that she missed him. I couldn’t find a reply to that message, so I asked him about it. He got furious and told me he didn’t see the need to discuss his past with me. I have an issue with this, because I always feel he’s hiding something.

Thank you!!