You need sex to become pregnant, so if you haven't it isn't possible. You're still young, your body is trying to work your hormones out and stabilize. This could take several years to occur. 'Pregnancy' symptoms are not tied to pregnancy alone. Nausea is a part of life, one we all deal with. Fatigue also will occur, many many times.
If you've never had sex then there's absolutely NO WAY you could be pregnant