Sounds like you two may have gone through the motions of "I'm committed to being exclusive with you, committed to not seeing other people," but at least one of you isn't interested in living up to that sort of commitment. Without both of you living up to that commitment, you aren't in a boyfriend-girlfriend relationship -- you're friends, you're dating, you're intimate, whatever, but you're not boyfriend-girlfriend unless there's mutual commitment to not see other people.
If this guy wasn't up to no good then why was he so secretive?
My advice is to not make that kind of commitment with a guy you've only known a few months. Your eagerness for that commitment sets you up for guys to "go through the motions" of making that commitment and then "break your heart" when it becomes apparent that they didn't mean it. Instead, be reluctant to make that commitment. Men will place a lot more value on something they have to work harder for. AND your reluctance will help you distinguish between those who sincerely want a committed relationship and those who just "go along" for the sake of ease and convenience.