There is this boy I like which I sit next to in...?

There is this boy I like which I sit next to in Religious Studies. Our teacher, Ms Fossille said that we will be sitting where we are for the rest of the term. (it is boy, girl, boy, girl...). We sat there and did not talk at any time, mostly because we couldn't as there was another teacher in here. The rest of the cl were whispering. He was talking to me but I wasn't listening. I was worrying about the Maths homework. He is usually really chatty, and might think I am boring next lesson. What can I do? How do I talk to him without messing up?