Why is my fwb acting like this?

Because right now you are the only sex he is getting he doesn't want to lose that to some other guy. Don't put to much into it because if he really was into you he would tell you not put that type of title on you. A women's heart always gets in the way of sex no matter how much you try to lie to yourself and others. This letter just shows you are wanting more from him. Why waste your time. You deserve love. Men can seperate sex and love us women can't.