That you are a bit slow on the uptake at times?
You have two possible options here:
Either he is interested in taking it further with you, and is very clumsily probing for your opinion on that. If his probing in bed matches his probing questions, you should think about finding someone more forceful and satisfying for your casual needs.
Or he has questions that a lot of guys get curious about. Ones that he trusts you to answer seriously and without getting ideas because you are firmly in the trusted but non-serious bed partner category. Sort of a sister, but without the whole "keeping it in the family" stigma.
How to choose which it is? Luckily for you, I am bored today, so have prepared a handy series of questions for you to answer. Answer them in order - the more important ones are first.
Does he sleep with other women? Or see other women? Or talk to you about other women? Does he refuse to go shopping with you? Is he there to listen without discomfort or complaint when you talk about other men in your life? Does he sometimes turn down a night with you? Is he sometimes really hard to get hold of?
If the answer to these is No, you are probably looking at the first option. If the answer to these is Yes, please pick option Two. As to what to do about it - well, it is your life, your call.