My tablet pen won't let me click?

Well, I have had my Wacom Bamboo Fun Pen & Touch for almost 4 months and this morning I was using it and suddenly the pen just stops working. It won't let me click on anything and it moves slowly and also it only works if I press real hard on the tablet itself. My friend told me I might have to alter some things in the properties but I just want to be on the safe side does anyone know what it is?