Boyfriend messaging this chick to "hook up" his best friend.

My boyfriend was over the other day and he was being wierd. He showed me this chick and was like "I'm trying to hook Corey( good friend of ours) up with her" she's an attractive chick she's pretty.. He also mentioned how he made out with her once in a closet.( 7min in heaven) Well he's obviously been messaging her. my SO wouldn't leave his phone near me when I was around. He went to take a shower and came back grabbed his phone( I wasn't near his phone) and I looked at him and he said " gonna listen to music while I take a shower" HE NEVER DOES THAT. Is he hiding something?!? We've been together for over 1 year and he's never cheated( that's what he told me) and he always says he won't.. Idk.. He sure was acting wierd. That wasn't the only time he grabbed his phone. He was babysitting it the few days he was with me.