How am I supposed to know if he's single or not?

[Desiree]

So this guy at my school, I have a crush on him.
I found him on Facebook, and only followed his page. He sent me a friend request and I accepted. I'm scared to make the first move, so I'm waiting for him to get online and message me or something.. :/ on his profile it says single.
But I was going through his pictures of him and his "girlfriend." And on her profile, her profile picture is a picture of them two together, and that was updated December of 2013, like one month ago.

He knows I like him, he even wanted me to write a letter to be sure that I liked him, because I never went up to him and told him. i always asked my friend to. So.. how can I find out, or should I just simply wait :/