Could my ex still have feelings for me?

I agree with Rad, he shouldn't get you mixed up like that because he's mixed up himself. He can have his cake and eat it too because he has a FWB realtionship with you and probably knows you wont go anywhere. Take a stand and tell him. Then he can make up his mind about it, but you cant make him choose one way or another. He will only do what he wants to do.