Become a man. Short of that, you need to assess the situation very, very carefully. Your question was only 14 words so I can't you a definitive next step, rather some questions you should ask yourself.
Questions like: Ok, my man who I am only "seeing" not long term dating or anything of the sort, already felt it important enough to tell me he may be homosexual. Is he telling me this because he is warning me that he can't get too serious right now? That it is inevitable and only a matter of time before he sets off to explore his gay curiosities? Also, how old is this guy? Is he new to dating in general? Am I dating someone who is just in the very early stages of forming an adult sexuality?
OR
Is he the kind of guy that just likes sharing all details of his inner workings and just because he mentioned he has "interest" in men, it's more anecdotal than anything else. Such as, "Sure we all live somewhere on the sexual spectrum. I find some men sexy, but hey, that just means I'm a free spirit. Pass the Doritos babe."
Question for you:
Am I the kind of girl that can handle and enjoy a relationship in the now? Meaning, who knows where this will go, my man can end this at anytime and decide to date my ex?
Perhaps the bottom line is thank him for being candid with you. Tell him you wish him all the best in his sexual explorations, but you can't be a passenger in his car while he's kicking other tires.
In other words, you can't figure out what's best for him, but you can work on finding out what feels safest, most respectful and enjoyable for you.
Being freaked out that he could find someone else attractive is kind of silly, be they man or woman...
Been there. If he has an interest in other men and is hiding it from the rest of the world you can't win. He will end up cheating on you with someone else whether it is with another woman to continue hiding it or a man to test it out.