Could I be pregnant on the Implanon?

Patient: I am currently on the Implanon and have been for 17 months. I have had a few problems with it I was on a 7 week period in April for example.However lately I have been feeling very tired, my lower stomach is bloated and hard. I have been getting fluttering feelings and headaches and I have been quite snappy and emotional over the past couple of months.I keep fit so am not over weight, but I have put an inch on my waist and gained 3 pounds over the past couple of months. I have been assured by my GP that the Implanon is the best kind of contraception to use. Could I be pregnant? I can feel the implant under my arm where it should be.