I Have Had Nexplanon 4 Months, I Have Not Had

I have had nexplanon 4 months, I have not had a period since I've had the insertion. I had a fever, nausea , and really fatigue the last 2 days which has now lead to dark bleeding I'm concerned about possibly being pregnant and now possibly having a miscarriage I do have an appointment to get this removed and plan to talk with my gyno but I need some sort of answers now...