I've been on the implant for over a year and a half now and I've never had any problems with it, I haven't had a period for over a year but I don't use any other contriception because I thought the implant was completely safe. Recently I've started to become more tired, going to the toilet more, losing my apitite which is unusal for me and constantly getting headaches and feeling ill and dizzy, I need help! Could I be pregnant?

No birthcontrol is 100% effective. So there is always a chance, though it is REALLY unlikely in your case. I would venture that you have an unrelated infection. Go to the doctor for a complete work up.