I slept with my guy friend but it seems he's still in a relationship after telling me he wasn't?

i met this guy at uni and we get on really well. when i first met him i saw a pic of him and his gf in his room and asked about it- he told me they;d split because he'd cheated on her. like a year later, one night things got hot between us and we had till 6 in the morning. bt it was in the morning that i noticed he had some different photos of him and his gf around his bedroom. i didn't ask about it because i felt stupid and very confused. anyway this was lke a month ago and we've been chatting on messenger, and even though his facebook page shows he's in a relationship, he continues to flirt with me and we have conversations but i'm still too scared to bring it up. i don't want to kid myself but at the same time, why isn't he telling me what's going on?