Can you be so scared of being pregnant that your body will act like you are?

Possibly. When a person is really anxious , one of the symptoms they can have is nausea, which of course also can happen during pregnancy. There is also a rare condition called pseudocyesis where a woman believes she is pregnant although she is not. In this situation she can develop various signs and symptoms of pregnancy. Consultation with a psychiatrist or other mental health professional may be helpful.