I Really Like This Guy In My Class

ok so i really like this guy in my class, i've told him i do but that was ages ago and i think he thinks that i dont anymore.. i have his msn but when i go to talk to him i just freeze and click off :| i hang around with his cousin who's like my best friend.. she says im obsessed- in a funny and cute way -i catch him looking at me in the corridors and in class. my science class has 4 desks that sit eight people. there's three ways to get through to the back, im next to the window with my 3 friends talking and he walks through the middle: as he got to the teachers desk he looked around, looked at me, grinned and purposely walked BEHIND me and my friends its a very small space inbetween us and the wall.. it didnt bother me until he started playing with my hair as he walked passed, i said to him 'WHAT THE HELL DUDE?' he turned around, smiled and said 'you get a haircut chris?' then walked away... WHATS THAT SUPPOSED TO MEAN? i really like him but i think he's going out with someone. what should i do >:|? xx