Nexplanon? Pregnancy?

I’ve had nexplanon in for 5 months, since the birth of my son and would always get a period and bleed for up to 2.5 weeks with no other symptoms. Now for the last couple weeks I’ve had sore sensitive breasts/nipples my areola are darkening and waves of nausea and intermittent cramping. My doctor wants me to rule out pregnancy but is that even possible? Since I’ve had it in for awhile shouldn’t it have completely stopped ovulation?