went on my boyfriend's facebook. Need advice:]?

[raspybook160]

ok so i went out on his fb without him knowing it was just by chance that this happened.. anyways i see a message from him to a girl telling her to call him on his house or cell phone.. (i've been living at his house for the past couple of months) we are always together. & he must call her when i go to work (he isn't working at the moment) He must call her then cuz i havent ever heard any phone conversations and then she says she misses him. & he hasn't seen it yet. Do you think there is something going on? ? am i buggin?
and why does this have to be on the phone when i'm not there? when i say were literally always together i literally mean it. we only part when i go to work. and i saw older messages from before because the convo had started early and he was talking about something else before but i cant see those ones because it is deleted.. he also commented on other girls photos when we were already 5 months together. saying "i'm jealous of the guy who gets to be with you, and your so pretty.." blah blah and we got over that. but seeing this message honestly does piss me off... what does a grown man have to talk to on the phone with a girl for? & its not just a hi how are you its probably those long ass hour conversations i just know it....