Possibly Pregnant on the nexplanon??

I know that it is unlikely to get pregnant on the nexplanon, but there is a hand full that still do. I been on it since March 30, 2017. Never had an problem with it. I will be having it replaced here before to long. For this whole month I been all out of wack. I been nauseated, just the thought of food can make my stomach turn even after I eat I just feel sick. My lower back has been killing me, my boobs are more tender, stomach has been cramping and smells are getting way stronger. I can smell the fishtank now as soon as I walk through the door. Also a week or two ago I have had slight bleeding just enough for a panty liner for 3 days. I have took 3 pregnancy test all came back negative, so I'm not sure if I took them two early or not. My sister & I normally have the same menstrual cycle and she has started and I didn't. Yesterday I did have some slight watery like period blood and same with two day. Just looking for thoughts and opinions. Have any of you or do y'all know anyone that has got pregnant before there implant was due out?