I was in school then all of a sudden i feel depressed and nausated and it keep happening throughout the day off and on, i'm usually a pretty happy?

If it doesn't pass: See your doctor to rule out physical causes and see a therapist or psychiatrist. Chances are it will pass, but if it doesn't have a game plan to contact someone you trust and respect to act in your best interests in the event you were to become suicidal. In that case you need someone to call 911 or take you to the nearest er. Hopefully it won't come to that, but it never hurts to be prepared.