Dear tatyanap,
Men who frequent nightclubs as regulars are generally players in my opinion. I believe they go to the clubs for the "variety". Not that there is anything wrong with that, necessarily. It's where he is right now on his road to growing up. Some of us girls do or have done the same. I do hope he is practicing safe sex, though. There is no guarantee that he is. And no way of knowing.
I have read the second part of your question too, and it sounds to me like you have a handle on this. I do understand your desire that all people be up front about things, but it isn't always practiced, although I personally agree that it should be. At least you are aware and you protected yourself with abstinance in the situation. So I probably don't have to remind you that you should always play it safe in encounters with romance -- which is not to say you should never have sex -- your sexuality is a valuable part of who you are -- but that you should continue to be discerning and engage safely , knowing what you know.