Hi i have the implant and find my periods come when they please. usually its every 3 months. i also get sore nipples, heavy boobs and a bit of a swollen abdo at the same place (tho thats probs just me gaining weight cause im a lazy git)
i have also felt exhausted and nauseous but i think its simply the implant...i have heard of it giving some women pregnancy symptoms, so i wouldnt worry :)
Go to the doctor and get a physical. they will know what is wrong with you!