Is he using me for sex?

My ex and I broke up about five months ago due to him kissing another girl when he was drunk (iknow its arguable). and he started liking other girls and, me other guys but we wound up back in eachothers arms- literally. We started talking again and fooling around and i have been waiting for him to ask me to be his girlfriend again. He keeps putting it off and saying that its confusing an that he will eventally ask me. Well its getting to the point where i am becoming frustrated and when i bring up the mtter of becoming his girfriend, he gets sortof aggitated and says im acting just how i was when we WERE dating, and that i always argued and stuff. i recently read on his facebook chat that he told his friend that him and i are "friends with benefits". Do i stay with him in hope of actually having a relationship, or should i eliminate all sexual reations until we are actully dating?