What Causes Nausea And Dark Areolas After Implanon Insertion?

I got Implanon inserted about 4 months ago. For the past month and a half or so, I've felt many pregnancy symptoms: extreme fatigue, frequent urination (i've had 2 UTS in this time), feeling flutters/pulsating in my lower left abdomen, nausea at some point most days (but never severe), lower back pain, and darkening of my areola. I've taken two home pregnancy tests and both have been negative. I know that these symptoms could be cause from the Implanon, but since the symptoms seem to be sticking around and worsening i'm wondering if Implanon might be affecting the tests?