Is it normal for my student to have a crush on me?

Hi, i am a higher secondary teacher. I am 27 and is happily married. I keep a close rapport with all my students since it's very necessary to be friendly with teens to handle them.I want to write about one of my favorite students. He is 18...a good boy,studies well, very well behaved,sincere in whatever he does and have a helping mentality towards others. He likes my subject and was always ready to help me when ever i needed it.He helped me in making subject magazines, in arranging an exhibition (he draws beautifully)typing my notes. ...We were very comfortable around each other. But for a past few weeks i am noticing that his attitude towards me has changed.He is no longer comfortable when he is with me, avoids my eyes while talking to me.But I have caught him staring at me intently many times when I am teaching. He becomes very moody if I talk and laugh with any other student. I am very much worried for him. He is my most favorite student. I can see he is distracted in class and that will definitely affect his studies.I can't believe that the boy who laughed and joked with me easily a few weeks before has completely changed. I tried to talk to him, but he is avoiding me. If he does talk he hastily mumbles 'every thing is fine' and runs away. It was one of my colleagues who suggested that he may have a crush on me. I was very embarrassed. But the more I think about his behavior... I don't know what to do..how to handle him...pls help me with your suggestions.. I want my best student back...