I think if you bet turn and he called and then you checked river, he'd be more likely to bluff.

I think after you c/c flop and then c/c this particular turn,he probably expects you to have either two pair or straights very often. Hands like 46, 56, 67 etc are definitely in your flop c/c range. I don't think he's bluffing here.

Folddd.