Iwant to know what are the causes

We can't diagnose online, not even doctors can, but we can tell you that a common problem is yeast, which you can catch without any sexual contact. It happens when your pH is out of balance. It's OK to tell your mother if you are a teen, and go get an over the counter treatment, ask a pharmacist, or see a doctor. You can see the whole range of 'vaginal discharge' type conditions if you start doing a web search on those words.