Lets say that he does accept you back as a friend with benefits (after all, this is all you were to him). What will you do when he finds another girl who he does want a relationship with? Let me assure you, when he finds his Miss Right, all his confusion will evaporate and he'll dive right in with her.
I'll guarantee that when this happens, you will feel a whole lot worse than you do now.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.