I like this boy and I'm sad...
Why are you sad about liking him?
I'm sad because he doesn't have a crush on me
I'm sorry you're going through that.  These situations happen often throughout life as not everyone we're interested in is gonna be interested back.  You'll find someone who returns your feelings for them sooner or later, I promise!
Really? with my luck? You should ask my cousin, she's a bit pessimistic.
It can be difficult to put our feelings out there for another person. If the other person does not reciprocate these feelings it is not the end of the world. Try to see the good in the fact that you had the courage to put yourself out there.