This guy sounds alot like me when I was 17 and was infatuated/obsessed with a girl.
"Sounding like me" means that on his forehead written in bold, black letters are the words "Warning: Thicker Than Rock."
That means that, as nice as you have been, you're probably going to have to be upfront with him and tell him that you do not like him like that and that his actions have forced you to cut off all contact with him.
However, in your private time, REMEMBER him in your prayers. You HAVE to do it this way because his emotions are so screwed up and focused on you that he's really not going to believe you when you say no because he wants to believe too much that you are going to say yes. He's going to be hurt when you do this, that's why you remember him in your prayers. That God will show him that only He, and not romance, can fulfill him and that this young man will turn to God to heal his heart instead of other girls.
That's the sad thing about these situations. If a guy likes a girl, and the girl doesn't like him back, MERELY mentioning it will destroy the friendship. I don't know why it works that way. Innocent and naive guys who have no experience (or game, as the world calls it) with girls cannot mention their interest in a girl unless they strongly believe there is a future (which you should do anyway). Innocent and naive guys who ignore this rule end up destroying the friendship with said girl because girls have a self-defense mechanism that immediately changes her attitude towards you.
The correct response for a guy to make after being told that we are not liked in that way is to give the girl appropriate space. Probably have nothing to do with her for a good month or so. That way she'll feel assured that you're not out to date her still and hopefully you've worked out your own emotions, providing she's still interested in rekindling the friendship.
Romance is such a tricky thing. The rule for guys when you like a girl is to ask God to make it ABSOLUTELY PAINFULLY OBVIOUS what His will is in the situation, whether you should go or not. And to be patient. DO NOT RUSH THINGS.
Yes, the abhorrent jerks who move faster than the speed of light do appear to get all the girls all the time (even, especially, the one YOU like), but one day he's going to wake up old and alone. Forget him.
You do not want to be a heartbreaker who uses girls for personal gain. Be like Christ. Besides, who wants girls that go for the arrogant jerks who have "flavors of the week", even if they are Christians and go to your church? You can do better than that.
And above all, trust in God. If it is His will for you to marry, He SHALL guide you and bring the right one to you in HIS time. And don't worry if you miss "the one" meant for you. God will send another one, and another, and another, and another and however many times more He needs to until you learn whatever lesson you have to in order to finally meet rather than miss your "one".
So the lesson of romance is to pray, seek God's face, trust in Him, and do His will.
The lesson for girls in situations like this is to be blunt and honest, but pray for wisdom and for the guy you just broke it to, that God would minister and pursue him.
And for guys, the lesson is to trust in God, don't rush things, and ask for His guidance and trust in His timing as you continue following His will.
To sum up: FOCUS ON GOD!
He's a great God who loves you and doesn't get ticked off when you tell Him you like a girl. Nor does He sit up in Heaven with a swizel stick seeing what evildoers He can smack around today.