Implant Worries

So I’ve had implanon since May 2016 and suffer with very irregular bleeding sometimes for months on end and then gaps of absence will follow, recently I’ve been feeling a little odd and my chest feels a bit tender. I’m paranoid and worrying that I may be pregnant, anybody have any tips on how to decipher the difference between symptoms and side effects of implanon vs. pregnancy or has fallen pregnant on this form of birth control and can tell me what to look out for?