Emma, you are growing up!
The changing discharge is normal with your monthly cycle as your hormones. After menstruation you should be dry with no discharge for a few days. You will then become slightly wet and the discharge will continue to get more. It is clear and gets slippery. The discharge may form strings between your fingers. When you are at your wettest and most slippery, you are ovulating. The discharge then turns opaque (milky or slightly yellow) and become sticky until it dries up completely before your period starts again.
What you are experiencing is completely natural. The discharge is cleaning the cervix and the type of discharge will determine if sperm can enter your cervix to meet the egg. It is only at the most fertile days when you are very wet and sippery that sperm can enter the cervix. This mucus also protect and feed the sperm while they wait for an egg.
Congratulations on picking this up.
You can use pantyliners or pads (not tampons except when menstruating) or cotton panties that will absorb it. Some women have little and it is not a problem. Other girls have a lot and have to wear pantyliners.
