What Causes Missing Periods, Metallic Taste In Mouth And Nausea?

I am currently on the implant and have periods every month but they are very irregular. This month I have not yet had a period which I thought maybe due to the contraceptive. Today I have a metallic sort of taste in my mouth and have been feeling a bit of nausea on and off all day, I also have been very emotional and tired over the last few days. I may be jumping the gun as it may die down tomorrow but I have been researching this and a lot of people have got pregnant whilst on this contraception, yet a lot of people also find that they get pregnancy symptoms?? Can anyone help me?!