For the last few weeks I have been feeling nauseous and throwing up, I have been very tired, lower back pain, my stomach has gotten tighter, I have had a constant headache and fever and always feel faint and dizzy I do take furicets for migraines when needed and I have had the nexplanon for at least 6 months but is it possible I could be pregnant I took a test about a week ago and it said no but I still feel very sick.