Well...you've done gone ****ed up now haven't you :/
Meh, just tell him how you feel and see how he responds. There's nothing wrong with changing the nature of your relationship with this fella. Just respect his thoughts and be open and honest about it. I wish you good luck.
Friends with benefits rarely work out. You both should have entered your relationship knowing that sex is all you wanted out of it.
One side nearly always wants more, whereas the other doesn't. This leads to heart break and the woman hating on men for a good century. (In most cases it's the female who develops the feelings, hormones and all that jazz.)
You could always asks him how he feels, however if he wanted a relationship with you, he would have one. He wouldn't just be having sex with you and also (probably) other girls. If you approach this subject and he doesn't having similar feelings, you can either carry on having non meaningful sex
You could walk away now and avoid getting too attached and involved and find someone who is willing to respect you and not see you as a sexual object.
I have been in FWB relationship and I got out as soon as I started developing feelings as from experience, it just gets too messy and you end up getting hurt.