How much should I be open to my students?

There was a student who worked really hard. He was not the smart one but he was definitely the most diligent one in the lower level class. He was always good in class, and fortunately my teaching way matched his learning style well. Therefore, he got good scores at the final exam. He got confidence and I thought it was all good.

HOWEVER, it was not all good.

There are some students who are friends with me on facebook. He was one of them. He was one of my students but not special to me. I shouldn't love some students more in front of them, but I can have some I prefer secretly. He was not special to me at all. He was a good student but not the one I wanted to keep in touch for long time. He was always eager to get attention from teachers, and I knew why. He didn't have many friends. He had some, but not enough for the age.

Anyway, once he became a friend on facebook, he kept leaving message on every my post. He clicked all the like, and commented as much as possible. That was little creepy. I wanted to be close to my students, but not this way. He showed too much interest in me and I didn't like it. He should do that to his friends.

One day, he called me on my phone. I was stunned and scared! I didn't give my number to him but he called me through my facebook. I didn't know that someone could call me through facebook. He texted me a lot and I replied some but I got tired soon. I was not his friend. I had not been his homeroom teacher. I might be the teacher he liked but I didn't want to get news from him every month.

He even tried to chat with me whenever I was on facebook. Everytime I logged in facebook, he sent me messages. Oh... even my ex boyfriend didn't do like this! (Because he knew that I hate that kind of behavior)

Another day, he wrote on my facebook that we wanted to be an English teacher and wanted me to cheer him. I wrote him back in English. He said in Korean: Teacher, please translate it in Korean. I can't read it. How ridiculous!

After that, I stopped to text back him and replied back him. I also found out he also sent lots of text to other teachers. Other teachers were afraid of him not having friends in high school. Also, they tried to keep proper distance from him.

I stopped everything. I disconnected friends in facebook, too. However, he kept sending me message by phone or facebook. He kept sending me asking to be friend on facebook. Oh, gush....

I almost forgot him, but time to time he sent messages even while I was in USA. Also, today, I got messages from him in facebook, again! Now, he is so CREEPY and SCARY. What if he did something wrong and blamed me for that?

Nevertheless, I don't like him. Now, I dislike him for all his doings... How can I do to someone who likes me? It is creepy although he is much younger than I am and I was his teacher.

What should I do? I don't want to be involved with him anymore...T_T Am I doing wrong?