Kate Or Kaitlyn???????????

My parents named me Kaitlyn. But a few years ago I started going by Kate, like on the roll-call teachers call Kate & everyone did. But now I'm older I kinda want to go by Kaitlyn again. Though everyone will think this is stupid, right. Because now I'm at high school there's to many Kate's and i can never get an internet username (on websites) with Kate cause so mandy people are called that. WHAT DO I DO?