please read

For a month now I've been with an amazing guy. We talked for a month before we decided to get together and everything was great! Or so at least I thought. I thought I was the only one he was talking to and such but, I wasn't. About 2 weeks ago he fell asleep and I had a gut feeling to get on his phone, so I did. I found some messages that I didn't quite approve of, at all. (Names will be left out) she would flirt with him, call him, snapchat, etc. but he wouldn't flirt back. It bugs me because you have to stay loyal just talking first before a relationship.