I'm 15 And Like Any Other 15 Year Old Pregnancy

I'm 15 and like any other 15 year old pregnancy is a big thing my questing to you is to help me to figure out what's happening I have noticed my stomach getting bigger and some different changes in meself like sleepy ,cravings , toilet more ,headaches etc but I have never had sex or near a boy or in contact. Can I still be pregnant I have taken a test but came back negative so I'm a bit confused