I am 13 year old and i have a bad smell coming from my vagina and sometimes it is itchy!

Sounds like you may have a yeast infection (thrush) or similar. I suggest you talk to your mum and go and see your doctor. I don't think you need to be worried, it can just happen. Nothing to be ebarrased about but doesn't need to be sorted out.

Good luck and help you feel better soon.