Could my Bf be cheating?

So ive been with my Bf since Novemeber. Today he told me his old friend went out for drinks with him and his friends a couple months ago! I said umm? U never told m that u meet up with her, & that just made me feel like he was trying to hide things; So i said i couldnt realy trust him, He gave me his Facebook emial and password to 'prove' i can trust him; At 1st i was like Noooo im not going to do that! because that why psycoo gfs doo & I know he wouldve deleted everything anyway. BUT my girl jus said, Just look because we both were curious. Ofcourse he dleted alot of messages BUT we saw in his sent back in Febuary he messaged some girl saying " Well he just has to learn that we r friends & I live in the USA no reason to block me " That right there made me feel like he was Flirting with her Or hitting her up tooo much that her Bf got mad ! It was in he beginging of our relationship , But what do you think????! -_-