I like this boy but I don't think he even knows that I exists what shall I do?
well bieng a boy, there are many variables. how good looking you are, how much makeup you wear, how shy you are, how popular you are, how much you hang around him, etc. if your ugly, well not much I can help you there. If you wear makeup that makes you stand out a little if your a teen. If you are shy, thats an obvious reason. If you arent popular, thats another obvious reason. If you dont hang around him or talk to him, how can he know you exist? Try troubleshooting and fixing what you find wrong and im pretty sure he'll like you back [just tell him you like him!]