They can be 2 separate unrelated issues. But if you feel nausea it is natural to feel anxious or depressed so it can be a chicken egg thing too. Your claims about your bowel movements not being normal may be incorrect, so you have to see a doctor to discuss this. It is abnormal to have a fear of people throwing up on you, so talk to your school counselor about it because you may be focusing on things that are best avoided.
Did you start taking a new multivitamin before this started? Any new eating habits? Eating closer in time to when you go to bed?
This rings of a gi issue to me especially when you speak of having trouble having bowel movements as of late. Stomach issues can go hand in hand with anxiety but I'd go from the gi angle first. Try some grape juice. My son with major gi issues and constipation was told in the ER to drink one cup of grape juice daily. It helps keep him 'regular'. He also takes a probiotic. These two things have greatly helped with his gi issues. If it doesn't get better, see your doctor.