Nexplanon

Is it possible to get pregnant on nexplanon? Since I’ve got it I’ve bled everyday and on the 21(Saturday) i was in my fertile window and I had sex without condom and since then I haven’t had any blood but yesterday I had some brownish looking mucus from me but no more since then and I’ve been feeling nauseous and I’ve had some bad headaches and For maybe a day I had some cramping not anymore then that day but I’m not sick and my stomach has been making me uncomfortable like I feel full constantly just bloated feeling but I haven’t really gained a big amount of weight and I have no other period symptoms. Any advice or opinions please ??? I had nexplanon put in on dec 11,2017 and my boyfriend is very fertile his family has a history of lots of kids even on birth control he’s worried cause of what could happen if I get pregnant on nexplanon i had a miscarriage a last year before my nexplanon and this feels like the same pregnancy symptoms I had then before I lost it I also take a daily medicine and my areola look a little different thoughts of some foods make me sick and my stomach at the bottom is a little puffy looking but my stomach if you touch it feels tight and hard